I would suggest a monthly rate maybe $75.00 per property and of course they would give you a 1099 at end of year for taxes.  

Tenant agrees to take care of the property and at end of tenancy return it in a condition as good as upon move-in, ordinary wear and tear excepted.

It has the charges we charge for cleaning at end of tenancy.

He is getting $30K up front, getting a payment from you each month and a final balloon at end of 5 or 10 years. 

I assumed you meant same unit occupancy but where one may use more, just because they have a tendency to, but yes I totally agree, if there are more occupants, that would equate to slightly more usage and should be charged as such.It does however get tricky when the water usage is "also" related to yard/lawn maintenance, that is why I simply stick to a per unit and then that includes water used during summer time for sprinkler system operation. 

If we put all the profits from each house into paying for the land, then the break-even-point comes at 14-16 houses depending on taxes at end of the first year and if any emergency draws are needed out of the profits.

When a owner pays for heat, tenants have a tendency to crank up the heat and then open a window to cool down.. 

See if your local market has a tendency to slow down this time of year or if it is not impacted.  

Call me old school but I stick everything in a manila folder and total it out at end of project. 

Our Landlord Association's up here have a tendency to be pretty structured, so we try to have a little more fun outside of the Landlord meetings.As Patrick said; there are more and more locals popping up everyday on the Forums!