Can't help about rent, I think it would also depend on where it is, basic condition of sheds and fields etc,
But as Arobwk says, be very careful, dont want to dicourage you, but either he may let you tidy it up, put a lot of time, money, energy into it, then sell, or as a situation i heard of, owner died, family came along and kicked tenant off.
Or on a FB group, someone was renting a place but owner was still using buildings, and then rented some to some troublemakers.
Unless you get a decent length of lease, it would be risky, unless you didn't put much into it.
Sorry for sounding a miseryguts, just warning of some of the possibilities