the age doesnt really matter, it is your sanity that you have to consider
i got my first foster, tiger when subi was 7 1/2 months, then i got bailey 6 months when subi was 8 1/2 months, then i got tiger back, bailey and subi when sub was 9 months, then tiger left and we got faith when she was 10 months. Subi never had any problems until faith and that i think was because we constantly had dogs coming in and out of the house and she was confused. so i have stopped fostering for a little while.
2 males are not a big issue as long as both are neutered. we have 2 males all the time in rescue and we have not had any real problems. it depends on also if both are agressive, this is a no no, but if you get a little one then you can raise them with montana.
sorry this is long and drawn out, two is definitly A LOT easier then 1. it is what you are comfortable doing and if you are ready for 2 dogs./