can i sue?

this is long and confusing story so i will try to make it short and simple.
My husband's mom own a house with 3 apartments connected to itwhere he has live off and on before in 1. well when katrina hit we had to relocate somewhere else and was wanting to move back there. his mom and him had made a verbal agreement to us move in 1 apartment if we did all repairs to it(some real big majors one...wiring, floors cabinets) the agree was that since she's on SSI she couldnt afford to put in money n it for repairs. ok my husband works offshore at least 20 days out the month so we was gonna have her boyfriend(his moms) do the work on it and pay him....well after realizing that was a big mistake cuz nothing was getting done, i ask my daughter boyffriend if he could do some well this cause major arguement because jealousy flare up(another long story). So then she says that we cannot move in there.
here the questions:
1. do we have the right to sue for repairs already done by us in there around $5000.00 just in materials. His mom says no because he file as head of household on his taxes aand claim losses on her house. she says no and we are just out of luck and cannot get a cent back.
2. what else are we legally entitle to back on this

“His mom says no because he file as head of household on his taxes aand claim losses on her house.”

How he files his tax return has no relevance to any contractual obligation between himself and his mom. I also don’t see how he would have claimed a loss on her house anyway.

“she says no and we are just out of luck and cannot get a cent back.”

Sounds like this was a verbal agreement. Hopefully you have receipts. You could certainly take the issue to small claims court and sue his mom. I can’t predict the result of the small claims suit, as it all depends on how it’s presented in court. You might want to just have a consultation with an attorney who could advise you how best to be prepared if you decide to go this route.