Hi, my son wants to play the sax and I can rent one from school for 50 a month but I just don't have that kind of money to put out for an musical inst. Hes a great kid with lots of talent and very smart too. I'm disabled and can't work anymore. I really wish I could afford it but can not now.

It takes a lot of work and asking around, starting with his music teacher. It's really a local kind of effort - strangers far away aren't going to give away a sax. Of course you can search on ebay and other sites for a cheap used one, and you and he can save up for it.
How old is he? Parents far and wide complain that they buy their children instruments after months of begging and swearing that it's the kid's one true passion in life, and they lose all interest in it a month later.
The time honored tradition is that someone who really wants an instrument hangs around musicians, mows lawns, saves whatever dime he gets to start out with a cheap old half broken horn. It shows he means it.

Craigslist, pawn shops, possibly used from a music store.

If you decide to buy a used one, take someone who knows often bad corks, or other issues can cost big money in repairs.

Also, if child is going to play in the band, in school, do they not still teach child to play?

But teachers are business people, who get paid for their time. So, would you want to do work, and not get paid. Lessons is how teachers do work. That is how they pay their bills.

You can ask people you know, to see if a friend or perhaps a older teen may have time and would work for less, than a professional teacher