You can also use something like https://www.bitrefill.com that allow you to use Cryptocurrency to buy gift cards from thousands of retailers and use their services, many have discounts too. 

To expedite the accumulation of reviews, focus on competitive market pricing, provide exceptional hospitality (aka.. go above and beyond to start... think welcome gift, etc), and encourage guests to leave feedback after their stay.

We had one incident where a tenant got divorced, mentally fell apart, received a dog as a gift and kept it locked in a bedroom all day.

The gift that keeps on giving! 

She later remarried, paid off the mortgage and I gifted my part ownership to her and still lived there.

I asked her, "How do you typically use this gift?" 

We intend to gift properties and money to our heirs and they can be investors and landlords or whatever they chose to do.Not sure I really want a financial planner telling me what I am doing is screwed up, but I will listen to other RE investors and any good ideas they may wish to share. 

If we can avoid paying a "gift" tax that would be great!

You could also offer a gift card to a local gym to keep things fresh for health-conscious renters. 

@Tim Simmons No, we don't typically give the house captain a discount, but we've started to give them some type of gift card if they're doing a good job communicating.