Do rehab on house, convert back to single family and bring it up to level of rapidly rising neighborhood.

There are several websites where you can look up data on cities and neighborhoods.

I am interested in buying two properties - on a scale of A-C, one in a class A neighborhood, and while I don't think the math would be quite there at the higher end, I'm open as far as budget, and another in a class B neighborhood that's shaping up well. 

LLP is mostly used by professional organizations that not allowed to form an LLC.From a tax perspective - there is no tax savings based on what state you will form and create the LLC. 

Are there a organized groups that seeks to prevent this?

Local Planning commissions in these hillside neighborhoods are notoriously difficult and lengthy to approve plans.

I looked at a 2-unit bldg. in a not so great neighborhood.

I'd say this is a B neighborhood.

The lenders will foreclose at some point and if you look them up, most of them are already in foreclosure by the banks.Also, an hoa having taken back 100 units is a terrible sign for the development/neighborhood.

I currently own a duplex that I am house hacking, however, I would like this next deal to be in a better neighborhood to attract higher quality tenants.