I am not sure of the exact frequency, we have a couple buildings on site that they service and they have access to those areas.

Typically if you are younger and making good money with your day job you can argue that asset acquisition is more important than cash flow (buying marginal deals but at higher frequency).

Change your rent frequency.

How many letters did you mail, over what frequency, to how many addresses?

@Stuart Fox is right regarding the low quality of tenants and frequency of turnover costs may negate any Cash Flow benefits you may expect.  

Your future buyers will be hit by that cost and impact their affordability.Check the property's flood frequency.

It would be immensely helpful if anyone could enlighten me on what to expect on the subjects of fire, elevator and water tower inspections (frequency/cost), building maintenance, insurance, property management, etc.I believe 5% each month and a 2-3 month fee for finding tenants, please correct me if im wrong. 

I sent out 5 rounds to all 30 houses on a weekly frequency.

The cost per mow is pretty low, but I do leave the frequency up to the person mowing (it's a neighbor). 

I work in conjunction with the team that reviews claim activity for the Program Participants and can offer that any costs increases due to claims activity are reviewed based upon claim frequency, severity and they type of losses submitted.