Somebody has to pay for water, trash, lawn, snow, roofs, windows, etc.

Cost of insurance, taxes, trash removal, lawn work, what other incidentals are there? 

Detailed annual expenses include:  vacancy rates, specific tax rate, 10% for property management, liability insurance, sewer, electric and gas, snow and lawn care.   

I recently purchased an occupied property and the tenant claims the previous landlord "promised" to maintain the lawn.

Detailed annual expenses include: vacancy rates, specific tax rate, 10% for property management, liability insurance, sewer, electric and gas, snow and lawn care.

Think of all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

Who maintains the lawn?

Not to mention that the income of 2+ units share the cost of roof replacement, lawn mowing, property taxes, etc. 

When his tenants can't cover their part of the rent he pays them to do work on the next house or to mow lawns at his current properties. 

Currently the rent includes water, snow removal, lawn care.