While it might feel like an extra charge to tenants, these packages often provide value that indirectly benefits the property owner as well—like reduced maintenance calls or ensuring the property is better protected.In my experience managing a large portfolio of properties, these fees are becoming more common due to the thin margins in property management.

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

We simply charged 1% service fee.. so if the coupon ( in those days was 15%) We dragged 1% and divided up 14% to our fractional owners..

How is PM charging you if the agreement is over?

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

Some try to charge an up front fee.

Most folks are charging 10% of the rental rate for monthly PM fees. 1 months rent for a leasing fee and couple hundred for a lease renewal.

And, if feasible, charge for parking!

I am in PA and yes, it is legal to charge late fees to your tenant regardless of Section 8 subsidies or not, provided the tenant's lease allows for them.

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