If not rented at fair market rent, this property will just count as your residence, not a rental for tax purposes.Structuring the property under an LLC or land trust could trigger a due-on-sale clause, so check with the lender before proceeding.To minimize risk, consult a CPA for tax strategy, weigh financing costs, and draft a legal rental agreement.

I built a house and it’s going to be difficult to sell as I have no equity in it because of Cost to build.

So I would caution everyone to make sure the replacement cost for your improvements will realistically cover your actual replacement cost in the event of a total loss.

There's no cost to use, and currently $25 fee for applicants. 

What add cost should they expect?

Just a fYI as that can be a pain (and a costly one)

Transferring the rentals into LLCs before marriage helps maintain separation and adds liability protection, but California’s $800 per LLC annual fee makes it costly.

While using financing does mean I don’t keep 100% of the profit due to borrowing costs, it allows me to take on multiple projects at once and operate in higher price ranges than if I were only using my own capital. 

Capacity and Tolerance. 1) Capacity: how many people can you comfortably fit in the property, is there room to add more, or add more value to the tenants to increase rent.2) Tolerance: How many people are you comfortable living with, if there are vacancies are you able to handle that.House hacking is an amazing path to homeownership, and a nice low barrier to entry into self managing your properties.

Good suggestions above.I would research the labor cost of a total resanding and recoating.