What are options for having our investors pay their share of this monthly fee?   

Some, like ours, focus on offering optional services such as renters insurance or washer/dryer rentals without requiring tenants to opt into a full package.When choosing a property manager, I recommend asking about the structure and purpose of any fees.

So, older homes have a higher frequency of claims as well as higher severity.

For most, this isn't a realistic option so they update some of the most important regions themselves and copy the data from other providers where they don't have coverage.This is a big problem with these big consumer-grade real estate analytics platforms—you don't really know the source of that data, its frequency, etc.

We offer a $200 referral fee, and have been considering increasing it. 

I'll add a few more things that can have a huge financial impact: required reserves, LTC (loan to cost), application or other upfront fees, and prepayment penalties.As a fellow flipper, I think it's important to have reserves, but they shouldn't be required as part of your funding.

The first few times, I didn't charge a late fee.

Quote from @James Hampton: How about a quick check before you have to charge a screening fee? 

Let’s say with your plan they make an extra $100 or $200 in fees and you lose $1000 or $2,000 in bookings.

Quote from @Jonathan Bombaci: This year, our management company, which oversees 700+ units in Massachusetts and New Hampshire, spent over $209,000 on attorney fees, primarily related to evictions.