However, because of my unemployment and age, I am unable to get a loan from a bank which is currently the biggest problem here.

there is no second level and its hard to tell by the roof and the age of house, if there was an expansion of part of the house at some point.  

After that you have to consider property taxes, income taxes, weather (both damage and mitigation), age of the house, HOA fees, construction (stucco vs wood, tile roof versus shingles), city utilities versus septic/well, location,location, and oh yeah,Location. :-) ($500k House in San Jose ca or on the farm in the Midwest.)

Looking at 2 other mobile home parks for sale in the area show rents from 395-450, for single wides, so there's room for increase from the current $350.Other than actual expenses and numbers, age and condition of units, insurance eligibility, what else should I be checking on?

Regardless of OOS, I want to see that someone knows what they are talking about, and they did some due diligence already.For instance:If you want me to invest in your MF property, I expect to see the OM with basic structure info, pictures, unit mix, financial Pro Forma, renovation information (w/roof age), construction details, utility specifics, HVAC details, flood zone, purchase price and date, comps, etc.

There is no budget for electrical or fixtures...which in a home of this age you will surely replace. 

Use similar comps; number of bedrooms/baths, stories, style of house, age, quality of schools/district, etc.  

Age of the asset, number of units, there are just so many factors if you are trying to gauge upside, you need to consider them all.

Congratulations on taking such big steps at a young age.

You are doubling your transaction side exposure, adding far stricter license law regulations, stricter accounting regulations, billing & bidding approval processes & much much more.By all means give it a go but the age old phrase you don't know what you don't know looks like it's going to bite you in the butt here.