All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
1- It is lawful for you to hire Muslim brothers (or your brothers) for the repairing of the house you have bought. You are not asked to write an official contract between you and them. But three conditions should be met:
First, the work should be a useful work and its description should be clearly defined beforehand as to avoid any possible disagreements.
Second, the salary or wage should be defined and clearly understood before starting the work as failure to do so might result in adverse consequences.
Abu Sa’eed narrated: “The Prophet forbade hiring a worker without specifying his wage beforehand.” [Ahmad]
Another narration reads: “Whoever hires a worker, he should name the wage he is proposing to him.”
If the wage is not specified, the worker should be given a wage similar to that of people doing the same job in that area.
Lastly, the outcome of the job should be lawful, and in this case, it is lawful for the maintenance of the house.
Allah knows best.