Anything purely domestically can never get away from a judges actual authority or the US Constitution Full Faith and Credit Clause.

I'm looking into renting out a bedroom with a private bathroom.I've done a price comparison and judging by the location, condition and size of the bedroom the ongoing rental rate should be about $840 (rental prices for bedrooms are absurd in my area).However, that price is not taking into account the private bathroom.

John, but another thing to consider is if you have a single policy for multiple properties, All of your properties will be listed on a single declaration page.

Most likely not and very few JP judges have knowledge in this realm as they are elected officials and there is no requirement to be an attorney. 

It is just the one time if you get the wrong tenant/buyer and judge it could be a real mess. 

I'd be wary of any seller who makes such a declaration. 

How do I judge the rehab cost?

If you are are negligent or doing something shady a judge can (and probably will) pierce the veil of your LLCs and go after your personal assets.

You could have sections thrown out by a judge that are deemed unclear or not enforceable with how they are written.No legal advice given. 

You talked about your mom not answering for the appraisal, is she living in the house, if so that might complicate things as the judge may not wish to make her homeless.