I normally do move-in fees in place of security deposits here in Chicago.

For example, typically if a tenant leaves the unit in good condition, we'll refund the full security deposit minus a nominal cleaning fee.  

I'd accept let them know you understand, you'll wave late fee for September, ask how much they can pay.. if it's at least 50 to 60% I'd say Ok and  your next payment will be on XXX date. and find out how soon they expect to return to work..

Outline all property management fees / expenses and who will handle + how things will get repaired. 

A realtor keeps contacting me with potential tenants, what is the proper/legal way to turn them down if I don't want to give referral fee?

So, for a flip that sells for $200k, you want to walk with $32k after rehab, agent fees, holding costs, etc.

Bigger spaces are easier to lease because I can afford to invest money into marketing or split a fee with a broker representing a tenant... however as these are a variety of small office and retail spaces, I'm looking for low-cost advertising solutions.  

Over the years they have been late a couple months each year paying late fees, have gone through multiple checking accounts and have gotten shut off notices for utilities.

AFAIK, the most you'd be on the hook for is $200 + court fees if you were to lose.

Borrower paid single premium is when the insurance company charges a lump sum at closing, rater than monthly fees that last until you hit 20% equity by amortization.