There are patterns too!, I have wanted to make the half slips, bras with the slips, panties , I did one bra and it did come out quite nicely, Mcalls, simplicity has the patterns, BUT you might find some poatterns at thirft store, or better yet you already have pattern, your own bras,panties etc, just trace them out and cut them out.
Go for it! and yes I'd rather buy the material, elastic, the eyelets and what ever instead of paying 20 or more for a bra! and you can make the support kind too!