I have dwarf peaches and nectarines...in double pots. Please check this link
to help you choose the right Peach tree
. Many varieties are self-pollenizer [except pollen- sterile 'J.H.Hale], though it won't hurt to have a second peach tree
. Here is a tip from the Sunset Western Garden Book:
If you don't have any space for another tree. you can plant 3 or 4 varieties in a single hole. Prune the new bare-root trees so sthat each retains just one primary branch-and point those branches outward as you plant the trees in the hole.