Of all the things that a person can do in their life do derive satisfaction, building an aircraft and then flying it yourself must be in the top five percent of achievements. That said it is probably one of the most popular dreams that are held by Americans. Here on eBay there are hundreds if not thousands of aircraft projects up for sale or auction every year. They fall basicly into three catagories, General Aircraft, Experimental and Ultralight.  For discussion here I am not going to subdivide those catagories into Sport License etc. This is not to be a warning either about what type project you wish to become involved in. I will give some general advice on each of the catagories and the pros and cons of each type project.

General Aviation Aircraft; this is probably the most difficult area to enter and for most people pretty much impossible unless you are able to pay someone to do the work. A general aviation aircraft can only be repaired, maintained, certified, given annual inspection and even flown by licensed personel. Not only must you have a valid pilots license to operate the aircraft but a person who is doing any type of work on the aircraft must also be licensed, this includes any airframe work, engine work even electrical repair.  These people have gone to various schools and passed tests given by the FAA to certify that they have the knowledge and ability to do the work, They are also in most cases expensive:)  For this reason unless you are very wealthy or have a license to do aircraft repair it is not recomended that you purchase a manufactured aircraft (Cessna, Piper, Beechcraft etc) to rebuild with the intention of someday flying it.  This also applies to hot air balloons that are not rated experimental.

Experimental Aircraft;  This is probably the most popular catagory.  The aircraft in "experimental" class include everything from exotic futuristic designs to reproductions of aircraft from the beginnings of flight.  They are constructed from materials that range from basic wood, glue and fabric to modern composites, carbon fibers and ultralight metals.  Powered by everything from half a VW engine to a 150k dollar turboprop #. Because of these variations in design and construction methods the experimental class of aircraft offer almost any degree of difficulty as well as a choice of designs that are so wide that anyone interested in aircraft can find their perfect match or dream.  The down side to experimental aircraft is that somewhere around 60% of all projects started are not finished by the orginal owner and around 40% are never finished at all.  There are many reasons for this, I think the two most prominent are the fact that building an aircraft (even a basic design) is a much bigger project than most people understand.  Many of the kit planes (parts in a box) or tube planes (set of plans and drawings and you go from there) advertise that you can build them in a couple hundred hours of labor.  This estimate is based on I beleive the fact that the people advertising them beleive that everyone has built numerous aircraft, possess a fully equipped machine, wood, composit, fabrication and welding shop :) And not only do the possess all this equipment but are expert at using it.  Do not misunderstand it is completely possible for a rank amature to build an experimental aircraft and build it learning as they go each of the disiplines necessary to complete the project. It is possible, but totally impossible do do in the couple hundred hours suggested by the designers or sales staff.  In todays market there are aircraft Kits (Glasair is excellent example) that come out of the box completed to a point where it is not impossible to complete them in the suggested time.  They come with the wings, fuselage, landing gear, controls etc nearly completed and all the builder has to do it basicly simple assembly to complete the aircraft.  This is over simplication of course but it makes the point.  This brings us to the second reason why aircraft projects are not finished, Cost factor.  When I was first getting started in building experimental aircraft you could build something like a Peitenpol or Fly Baby for a few thousand dollars. Today a Glasair lll turbocharged and pressurized can cost over two hundred thousand dollars.  There are still numerous designs that can be built for much less than that but the days of an experimental airplane for two or three thousand dollars are pretty much gone.  There are many other reasons for a project not being completed, they range for a person just giving up since it was much more work or much more complex than they had expected to the reason it was not completed was it was a years long project and the builder just up and died of old age:)  Allot of us Areoplane builders are becoming old men:) For this reason there are some excellent buys on the market for some very nice kits or projects at a very reasonable price.  Just remember that the workmanship on whatever project you decide upon is very important.  So many times I have seen someone buy a project and then discover that it would be easier to start over than to try and correct the problems, errors and constructions methods that were done by the orginal builder(s).  This is especially prelevent in composite aircraft and aluminum rivited designs.  So if you are considering buying a partially completed project be sure to do the research on the project, find out the experience of the builder, find out if any inspections have been done on the work to date, talk to others in the area where the plane is located, in many cases the local EAA group will have someone who is familiar with the project, and if not in many cases they will willingly go take a look at it for you either free or for a small fee.   You can find the Local Experimental Aircraft Association  (EAA) listings and usually contact number at eaa.com Even if you don't use them for my suggestion its a great organization to belong to if you are considering building an aircraft.

Ultralight Aircraft; The last catagory is Ultralights, they again vary tremendously in design and cost. The orginal concept of an aircraft that weighted 254 pound or less and stalled at 20 miles an hour or less, carried only one person and no more than five gallons of gas and most importantly could be flown by an unlicensed pilot made them a boom business. There were hundreds of small and large companies who built them. They are a fantastic amount of fun to fly.  True you are limited to "around the patch" or very limited cross country flights in basicly calm conditions but the joy of what can only be discribed as basic but true flight is only obtainable in what is basicly a powered kite.  They range for beautifully simple designs like the Easy Riser (in its various forms form weight shift hang glider to lightly powered) or the techonologied advanced designs of Mitchell's A-10 wings and the Mylar covered Falcon  to the lastest versions that have fully enclosed cockpits, highly relieable engines and standard three axis controls.  These are wonderful aircraft and can be built or repaired with minimal experience or knowledge of tools. Most of them are also easy to fly due to low speeds and forgiving designs. A note here, there are ultralights that are of a higher performance level and are difinitely not for a beginner pilot.  The envelope of what is considered ultralight has been stretched with new rulings and pilot certificates. It is wise to check on where exactly a given plane qualifies in the ratings.  Now the down side.  Most ultralights are made form bolted or rivited together aluminum tubing, ripstop nylon cloth (sail cloth) and aircraft wire. The aircraft wire has the longest life span. Aluminum tubing can lose its strenght through age and stress, it can also deteriorate through unseen  corossion inside the tubing.  Rivets can loosen and corode as well.  Sunlight destroys the fabric covering of the wings.  A set of sails (wing coverings) can wisually appear to be in excellent condition and actually have only 20% or 30% of the orginal strenght.  I have seen ads on ebay for a Rally weight shift that was built in 1970 or so that the owner said was all orginal and in excellent condition. It is highly unlikely that this airplane was airworthy if the fabric alone was that old.  Unlikely airworthy is not what you push the throttle forward and climb out into the sky with:) not if you plan to fly more than once.  Of all the aircraft I have discussed the ultralight is the most important to check over thoroughly. The reson for this is there is no requirement for them to be inspected, maintained or in any way certified airworthy any time during their lifespan.  Make sure the materials are all in excellent condition, that the fabric is not aged or sun affected (ultraviolet light from sunlight destroys the fabric) that the engine is running properly and the controls are all functional.  The nice thing is that ultralights are in most cases easy to rebuild, the tubing is available, sails can either be purchased or you can have a marine sail loft sew a new set for you.  The engines are simple to rebuilt and most everything on the plane is easy to understand, exaime and repair. Once again do your research, make sure that what you purchase is going to be airworty either at time of purchase or you understand that it needs rebuilding and you will do necessary repairs before trying to fly it.  Remember the most important rule of flying,  Take offs are discressionary, Landings are mandatory. And the Sky even more so than the Ocean is completely unforgiving of ineptitude, carelessness or lack of experience....