I've collected thousands in security deposit from my guests who've caused damage.

The building next to yours looks much nicer and has THREE security vehicles parked in front.

I would upgrade properties every 12-15 months as allowed by low down payment loans if my significant other wasn’t risk adverse and opposed to moving.

.: The applicant needs a social security number or an individual tax ID number (ITIN).

If you do have to move because of a job, you would be safest (in my opinion, i am not giving legal advice or financial advice), i would sell that property to ensure that you did not just purchase with the goal of moving out early and taking advantage of lower rates and lower down payments for purchasing your home as a primary residence. 

Don't accept ANY partial payments.

@Marcos Carbi  If you want to allow a payment plan, Tell them this is the best I can do:Pay $xxx cash by tonight at 8pm for November's rent. and then beginning Monday Jan 20, pay $450 each Monday (in cash?

We have secured a home equity loan against our home (which we own out right with no mortgage payment).

I completely agree with @Ashish Acharya's points about the cost-effectiveness of a HELOC and the potential credit implications if it’s secured by your primary residence.

It is what is left after snow removal, cutting the grass, utilities, tenant issues, parking lot issues, property taxes, mortgage payment, etc. that make a difference.