However, I am considering working with local realtors to identify  properties with potential at good value and hire my own General Contractor to get it fixed (the BRRRR business model) 

Preferably in Multifamily, but would also consider other asset classes or development projects.

Zillow openly explains this at https://www.zillow.com/zestimate/ and publishes their median error rates and other stats for some major metro areas at https://www.zillow.com/zestimate/#acc.The good news is, it's relatively easy to validate how accurate it is for your market:Have your realtor pull 50 or 100 active and sold homes in the market/neighborhood you want to analyze.Compare actual asking and sold prices to the Zestimate for each one, put them in a spreadsheet, and develop some averages. 

MD does have a I think called "rural development loand" which is really popular here in Sothern Maryland and covers 100% of the cost of the home. 

To start, I'm eyeing foreclosures and I have identified a couple attractive ones (in good school districts, right price point, etc) and I intend to try and get a walkthrough on those properties.

How did you identify and begin to build a working relationship with a portfolio lender?

Are you a developer, are you a contractor, what skills do you have that will aid in your investments? 

Develop a relationship with a couple of local HM lenders.

I have developed a very good marketing pitch and I would like ideas about how to attract serious investors.

The  purpose of your contract will be to identify the price the seller is willing to accept, a deadline, and ensure that you can't be squeezed out.