It's very hard to spit ball numbers on any type of development project because every town has different restrictions and every site within each town is unique.

Make sure to read the HOA bylaws and verify if there are any rental restrictions on the property.

But I've found that in the areas where I feel comfortable buying a property that I think will rent easily and appreciate well, there are a lot of HOAs that have rent restrictions.  

I would also like to know what restrictions apply to a note holder that wants to negotiate the terms of the note with a borrower and rewrite the note.  

That could leave the tenants with a little less peace of mind than they desire and you could inadvertently send them packing.You may want to discuss your current restrictions or lack thereof as it relates to the current owner executing a long term lease with said tenants which you then have obligations to as the new property owner.  

HUD homes are popular targets for wholesalers/rehabbers specifically because there is No resale restriction.  

Your advantage is not the restriction of information (as it was in days of old) but now, the dissemination of information, along with the interpretation.  

How restrictive is the zoning in Philadelphia for SFH to MFH conversions?

I don't know what the rules are for Facebook contests/sweepstakes, but there are some restrictions. 

There are lots of restrictions & pre-approval for FHA needed with condos.