Our current mortgage terms include a late fee after 5 days, so they’re already paying extra each month and have to split the total monthly payment up between 2-3 payments when they get their pay check.

That house won't have a profit for 3 or 4 years now. As

I'm only barely a millionaire.

I had a STR in another market get shut down by zoning, so I put construction workers in there on a 30+day stay over the summer and now have a MTR tenant to keep the lights on through May after which I'll sell since I have no guarantee on having another 30+day contract next summer.

An example of that is tenant must pay for additional electric over flat fee / flat limit since now there is 2 occupants in the home instead of originally one.

If it’s your primary residence, a HELOC could be a great option.

I have a tenant in New Hampshire that I am in the process of evicting.

If you are hoping that this property will stand on its own with you living in it and not having to put your active income into it, then it might not be the best option for you right now. 

how is rental market in that area these days? 

Most common is a 5-4-3-2-1.