A big problem on the BP site when people ask for advice when dealing with Multifamily properties is not identifying which classification of multifamily they're seeking advice on.

On that note, what site and or public records entity should I be looking at and how much and what kind information is available there?

Calculating my ROI has been complicated because I don't know if I should use purchase price or current value.  

If they redtag you then you need to bring it to code with permit (70 West Hedding, planning dept).https://www.sccgov.org/sites/dpd/DocsForms/Documen...Sam ShuehCupertino, CA

I want it in person to avoid complications.

As long as they are patient, licensed and willing to help you (and they should since there is a possible commission at the end of this rainbow).I would suggest starting with one of the national realtor sites (zillow, redfin, realtor.com, etc), search for multi-family properties all over your area, pick one (anyone that looks interesting) and call the agent to get details. 

there are multiple sites that various NH towns use. 

The representative informed me that because there was already a paid advertisement for that building on the site I was not allowed to post on my own and I had to contact the property managers for the building.Has anyone else had to experience this kind of runaround and hassle just to list on either of these sites?

Also factor in on-site coin  laundry bringing in another $150 a month and garages bringing in $150 a month. 

As for underwater, never fully trust info from third party sites.