I find that putting a utility cap in the lease agreement they sign and calling their attention to it really helps make them more aware that they'll have to pay for excess usage so, fortunately, I haven't had to actually bill anyone yet, but the language is there if I needed to. 

If things start getting tight, you can always switch to doing work for clients too in order to raise funds. 

It could be that the decision makers were not aware of the ceiling on your budget.

I would raise the rent. 

I was aware of the egress requirement, but was not considering the door size or ceiling heights.

Putting in a ramp, adding grab bars in bathroom, raising the sink height, etc.  

Now, people are fighting back to appeal the raises. 

What legal requirements should I be aware of?

If there's one thing to be aware of, expect the unexpected.

But also be aware it appears their platform has changed in recent years.