Gifts received are not taxed in any way on the receiving party.

I am wondering if this would cross any legal boundaries, as I am not an agent, and whether offering a gift card instead would be a much safer avenue than a "referral fee" to advertise this reward. 

@Zachary Martin There are several pitfalls you will need to avoid - the biggest one off the top of my head will be avoiding the mortgage buy-out being classified as a gift.

But I can say that you'll have trouble with the IRS on a 0% loan: the rate discount would be taxed as a gift, I believe.

@Bill Exeter if I were to acquire the property from him in a gift equity transaction would I have to wait 2 more years after this transaction to be eligible for the primary residence exclusion even though I have been living here for almost a year?    

She would owe gift taxes on a gift that large in a single year.

Reason being that a $1 "sale" is really a disguised gift.

Some promo gifts that come to mind.KeychainPenCoffee mugCalander

They are getting Tenant Appreciation Gifts for staying during the construction and signing a 12 month lease.

I would also ask ur recent tenants what brought them there and make an incentive for ur current tenants that if the can referral someone that actually gets the apartment they get a discount on rent/gift basket.