Welcome to YT !!!
We have 2 and we love it. We got them a few months apart, one is 6 weeks younger than the other, both are female.
Many people on the site feel that 2 is the perfect number.
My 2 cents: it seems to me the boy should get fixed. God bless you for considering the rescue route. By adding a second, I'm sure you've considered:
1) TWICE the work
2) TWICE the EXPENSE (it adds up !!)
I think it's worth it. My wife had an "only child" before we got these two, and she says she always kinda regretted not getting her a playmate...
I hope this helps, good luck !!!