We have used both brass and stainless steel with good results. Both are rust and corrosion resistant. Stainless is harder and is usually somewhat more economical than brass. The quality of paint and the number of coats will greatly influence the durability of your boat. All seams should be fiberglassed inside and out for strength and to seal the joints.
Epoxy resin is the best and the most expensive.
Polyester is the most economical and the easiest to obtain, often Bondo polyester resin can be found at auto parts stores. When using polyester resin, mix one tablespoon of acetone with each ounce of resin to increase the penetration and holding strength. Actual construction time in general is 10 to 12 hours for the average novice. As a weekend project, on Friday the sideboards and bottom would be sized and scarfed. On Saturday the boat would be assembled and the seams fiberglassed.