mother in law wont pay

This summer my mother in law got an estimate to have a deck built I suggested she allow me to do the work and loan me the money that the contractor was going to charge her. I would then pay the money back over time effectively giving her the job for free. She backed out after the work was completed and said she was not going to give me anything. Allthe work was completed legally meaning all permits were drawn and all work needing inspections were approved.The work was done in michigan and the balance is 2700 dollars do I have any legal recourse

Based on your post that permits and instructions were done as required, I assume that their was no local requirement for you to be licensed as a contractor.

If this is the case (license NOT required), then you probably have a valid Small Claims case against her to recover your costs (and possibly your labor). You will have to show that the claimed $2700 was reasonable.

If the local jurisdiction has a requirement that this work be done by a licensed contractor, then you probably would have a hard time recoverying in court.

However, you have a bigger issue to consider.... that of pursuing litigation against your mother-in-law and what (if anything) this might do to your relationship with her, her family and your family. If you have considered these potential liabilities and wish to go forward, I believe that you have a valid claim.