You need to get the frame and parts at wholesale prices to make any kind of profit. You can add 50 bucks to the total cost of buying everything when you sell the bike but you will only make 50 bucks for spending a couple hundred, and what's that going to get you some gas and beer? It won't get you enough to buy more frames and parts you will end up losing money in the long run. Unless you can buy everything dirt cheap then you can mark up the price of the bike more than just 50 bucks. You would need to buy from a distributer to get that kind of price and I believe you need to be an incorporated business to buy from them but I could be wrong on that.