I charge them a demand fee, like an option. 

Real estate is the better option no question.

The other option is a water tank.   

@Lucas VreekenTypically a reit will pay dividends and has to distribute most of its earnings each year and you will pay taxes on that money earned each year.There are r a lot of passive investing options available

I have been looking into purchase options, but I might consider a lease option because it wouldn't go against my DTI when I purchase another home. 

Any suggestions on which option should i choose?

Seller finance would be your best option in a market like Florida if you are looking for it to cashflow right away.   

Especially going the low down option you will get the best bang for your buck. 

If you're open to less equity, this option would make your home more attractive to buyers depending on your rate.

I would still want to sell as an option in a year or so.