I expected this to be a popular question, but I've looked around and at least on google almost all answers look like they were written by the brokerage marketing departments.

I got a call from the police department that there was a problem at a small mobile home park I manage.

Your first step should be to call your local zoning/code enforcement department.

I started off the same place years ago and also was referred to the commercial lending department. 

You want at least a 30% margin above costs and the NOI needs to be enough to pay the debt service after stabilization and then some.If the project looks feasible from a financial standpoint the next step is to check with the city or county planning and zoning department to get an idea if your concept will work, if you can build what you would like to build and what is required for all approvals including site plan, building permits, proffers, water/sewer tap fees, bonding requirements, inspections, setbacks, lot coverages, parking requirements, height restrictions, C/O process and time frame for all approvals.You also need to check with the utility companies and get an idea of availability and cost estimates from them for water, sewer, power, gas, cable, installation and connection requirements, tap fees, hookup charges, transformer location and relocation, power line and power pole relocation issues.

They have a very strong commercial department and will lend on properties within 100 miles of Lowell MA (which is most of NH).

She is in the process of getting one now through an architect/engineer but is worried about fines and fees that may or may not come into play from the Building department. 

Often 75% of the labor budget on small repairs is draining and refilling the sprinkler system which you will have to do on your five year anyways (where there's a fire department connection at least).Finally, go to NFPA.org and register.

Not familiar with your specific town, but the building department should be able to answer your questions.

Go into the Building Department/Planning Department and confirm that a Three Family "Use" is allowed in the zoning district and ask what the process is to convert it.