Talk to any Portfolio (Asset-based) Lender.

I meet investors who started with TK just to get into the game and then did BRRRR when they had a nest egg of a portfolio. 

The last time the house sold was back in 2010 for ~144k. 3 family house in question has its issues(older home, older heating systems probably)  but I would like to own it as it would: 1. eliminate my driveway/snowplowing issues 2. add to rental portfolio 3 increase monthly income 4.

This is not a VA loan its just a small local bank and they keep these loans within there portfolio. 

Echoing what @Andrew Beauchemin said, you can find out owners of buildings by looking at property tax records on your county's appraisal site. if the owner is a LLC (which is usually the case for larger multifamily), go to your state's secretary of state website and look up the business in the business records search. i'm not familiar with pennsylvania, but that's how every state I've looked at before operates. there is usually an agent of record who oftentimes is the owner, however, for a larger, more sophisticated owner, it could easily be a lawyer or someone else.if that fails, a broker is your best bet. they'll have the relationships with owners and other brokers you need. as others have said, it's hard to go off-market without a track record, but maybe by showing your current portfolio and explaining your desires, you may win someone over :)

I have been looking for reasonable lending options to continue building my rental portfolio past 10 conventional loans.

This will help us build a long term portfolio and still provide enough to make a Little now.

I take that to mean that your firm sells portfolio packages of bundled secured notes and then turns around and issues loans on real estate.

However, if you go with an on balance sheet loan (portfolio loan) through a community or local bank you should be able to get a product with no seasoning requirements. 

I don't technically qualify for FHA or conventional loans, so I'm hoping to explore potential other options for financing, perhaps portfolio lenders at smaller banks, perhaps a partner that would like to team up on a property?