@Nicholas Gray Don't do it. It won't get done. Instead, pay him the going rate for every time you order snow removal. I.E. Come the first serious snow, say I will pay you $20 (or the going rate) to remove snow if it is done in the next 24 hours. I wouldn't take it off rent and devalue your lease. Instead pay him like you would any snow removal company.
I echo @Ryan Blake . First, what if there is no snow yet you are giving rent breaks? Plus, rent breaks aren't a writeoff like snow removal costs are. Don't do it.
Why not put "snow removal is responsibility of lessee" in your contract?
NOPE...no way...do not start trading services in exchange for rent....very slippery slope and the landlord usually gets screwed. Tenants rarely follow through with the service or do a crappy job....nope....
The rent is the rent....PERIOD. If you want to hire a tenant to do anything, you pay that as a separate expense.
Liability is an issue in this case too......
I've never had a landlord provide snow removal. Even in a duplex, shoveling was like mowing....my job.