About homebuilding. First a question, do you want to build or do you want to sail? Homebuilding is a lot of work, and it demands a suitable place to work. You will spend a lot of hours building, which cuts into your sailing time or time spent with your girlfriend.
A second point. If you want to build a boat yourself to save money, you should know that fitting the boat out is the really expensive part. Sails, lines, halyards, trampoline, blocks, cleats, perhaps professionally make rudders and daggerboards, mast, travelers for the jib and main, standing rigging etc. If you want to save substantial money, you need to buy a wreck of a cat with gear still usable on it (mast, beams, traveller, blocks, cleats etc) which you can use. Homebuilding your sails can also save substantial money. Are you an expert scrounger with time and the dedication to go trough all this?
Buying a used boat is probably the cheapest and most enjoyable way to get an F-16, unless you have special interest in boatbuilding or doing thing yourself for some reason.