I am looking in the downtown area as well as east campus and West A neighborhoods, but I am not married to any of these neighborhoods.

To the best of my knowledge (if I'm wrong here please correct me, someone), since the HUD manufactured home framework came out in the late 70s, multi unit manufactured homes have never been financeable with fannie/freddie/fha money, meaning no one ever made them, and probably no city ever allowed these types of modifications because they would create potential blights, meaning there's about a zero percent chance that any of the stuff making that thing a multi-unit has permits, is remotely close to being up to code, etc.

Even so, I'd be hesitant to buy one of those Downtown without putting serious consideration into the upcoming tax reval, which could cause property taxes to soar for owners in this part of the city.However, not all hope is lost if you're willing to entertain options elsewhere in Jersey City.

I live in this zip code and I feel that there are a lot of elderly people living in this neighborhood which means there will be a high turnover over the next 5-10 years.

I have the forms for tax abatement from the City, but have not started those (should have been done before this started).

Leo, take your time, learn all you can about screening, and buy a property in a good neighborhood, then do some more screening. 

Although I am primarily from La Mesa, with divorced parents I also spent lots of time in Hillcrest/North Park/South Park and truly watched each of those neighborhoods gentrify.

Friendships are formed and its nice to pick up a phone and talk to a local investor when you have a state or city specific issue or just to go over a deal or neighborhood. 

From the City of Philadelphia's website: An Activity License is needed to conduct business within Philadelphia.

It takes a ton of knowledge and patients dealing with contractors and the city for permits.