Lease and contract work forms/advice

I have a 4-plex in Phoenix AZ that I decided to manage myself (no local property manager). I decided this because one of the tenants has about 10 years experience as a maintenance man/custodian as his day job, and he offered to assist me part time on this property on an as-needed basis.

He’s agreed to be an independent contractor, and will bill me on an hourly basis for any work done. All work will be pre-approved by me before he starts. We both agreed it will all be recorded in writing, through regular mail or email.

What contracts or agreements do I need to have in place with this person to cover myself legally in the long run? I’d hate for him to one day claim I didn’t compensate him well enough for the work he did. Also, how about health/hazard insurance? If he gets hurt while working on the unit, could I be held liable for the medical bills?

Any advice would be appreciated.