I am considering doing this but should I charge a fee to write up and get the lease addendum signed?

What costs/fees should I look out for?

However, if that effort fails, the local agent is equally liable – criminally and civilly – for any fees, fines, etc. associated with the property." 

It may sound nice to pay a 6% management fee but the extra fees can add up to be more than the other company that charges 10% with no additional fees.

That being said, there's more to the equation than just rate and fees.

I am looking to connect with the investors there as the promotors are continuing to take Asset Management fees to the tune of $450K a year (on top of PM fees) even when their payout to the investors is around $20K a quarter (not meeting preferred) and the overall fund is negative about $450K.

The pet fee or deposit for the move in of 2 cats (you did charge one, I hope) should have just about covered the extra anyway.

Charge a fee for the ESA.

If the bill is $100 a month split between four units, increase it to $120 and charge each tenant $30.How to calculate charges.

Have you considered a flat fee MLS listing as a way to gauge interest and possibly sell?