My son has decided to play in the band at West York. His instrument of choice?
The tuba. 
My thoughts are, if you can hold it, then try and play it.
Luckily, the school said they have a tuba that he can play at school and they will let us borrow a tuba to play at home. Prevents us from having to lug a tuba to and from school.
We got a bit of a reality check this week in a letter that was sent home from school. Lose the school tuba, pay $2,500.
Ouch.
Luckily, a tuba is hard to lose.
You are lucky that they had even one for you to use. We have had to buy or rent any of the instruments our kids have played. We soon figured out that it was better to buy from the get-go because the high price of renting was just money down the toilet. At least with a purchase, we can recoup some of the cost later by selling it used. (We prefer to buy used instruments, too. I mean, really. A secondhand trumpet is just fine for a 4th-grader, don'tcha think?)
Has anyone else figured out the tricks of keeping things affordable for young musicians?