I actually paid him with a business credit card so I contacted my credit card company to issue a chargeback.

I would suggest that you make some business cards for the property (not yourself per se).

(which can easily make up for the inconvenience) Another thing we did was to offer a $200 gift card (or some sort of incentive) for resigning their lease, and for many that was enough to keep the same tenant another year. 

I just set up a lead generation squeeze page and ordered some business cards. 

Now you have a "credit card" like loan based on your property equity.

That's okay if you need someone to manage for you, but if the facility takes cash I would switch it to credit card and auto-draft only (maybe checks too).

I’ve been in contact with PostCard Mania but their minimum deal is for 2500 post cards and I just don’t have that large of a list yet.

Or should I go with just getting 2 or 3 secure cards  to start building my credit and ignore taking care of the debt (credit score-610)?

I've been thinking of mailers, but I don't know what gives the most bang for the buck (and the second I started researching, I got bombarded with those little yellow card mailer ads).

If I decide to move to another agency that offers more training and support for a new agent, after they put in the time and effort to get me all signed up, business cards, website, various accounts, etc.