Whereas I cannot help with this problem, when I owned properties in Puyallup, we never had this kind of restriction. 

Municipal-run utilities can impose a lien on the property. 

Yes the modular units are restrictive in size.

Once you see a piece of land attractive to you, call sellers and ask all the questions you have as they may already have the answers (for example: which municipalities you have to go for permitting, how much of the land is buildable, any restrictions, etc...).Once that is done, go to the building department and share with them your plans to build and what will be required from you to make your vision come true.

I have taken a course of mobile home investing and they made it very clear to stay away from investing in a Mobile home in an age restricted park (55+).

Once you know the down payment and expected closing costs you can work backwards to see the amount of property you can afford.Condos are a nice place to get your feet wet in REI since a lot of the big expenses that you may incur are wrapped up in the HOA fee you pay every month vs Multifamily were you need real reserves and you are liable for all repairs.Also, you need to address possible restrictions in these 55+ communities in regards to purchasing and renting.

A couple things you would want to investigate further are the zoning (if duplexes are allowed), how utilities are setup (individually or separately metered), and any other restrictions on long term / short term rentals.

But....I would still ask someone at the Hoa if they have ANY rental restrictions.

Hmmm, I guess I thought of a few more Absentee Owner/Mgr Assemble lots Assumable Loan Boarded up Property Bought other Property Burnt Out Landlord Buying New Home Condemned Property Competitive Property Deferred Maintenance Delinquent Mortgage Development Ready Disappearing For Sales Economic Problems Fire Damaged For Rent Signs & Ads FSBO Signs Good Area - Ugly Home Hard Money Loans House Smells Bad Inexperience - repairs Investor - No Upside Lack of Concern Landlord Problems Location is bad Low Equity Property Management Problems MLS-Expired MLS-Junker Properties MLS-Listed too long MLS-Motivated Seller Negative Cash Flow Neglected Property Non-Qualifying Loan Old Property Over Priced Property Owner Will Carry Private Mortgage Property near yours RE Taxes too high Restrictive Covenants Rundown property Sell personal property Seller worried - taxes Subdivide - sell part.

The main restriction is that you'll need a contractor that is licensed with the City of Scranton (at least the last time I checked).