However, you have to invest in specific communities where they are encouraging development.

My recommendation is neighborhood specific.

My strategy incorporates asset protection measures like LLCs, specific trusts as well as professional property management to spread risk and ensure quality operations.As well as using tax codes to my benfiitSection 179, IRC Section 162, Cost Segregation and Bonus Depreciation and later 1031 them out for larger projects. 

Can it be done, heck yeah but it's a specific business model and does not operate as say a good running STR business. 

The mold remediation companies should have the skills to identify the source, suggest a solution, and give you a bid with a guarantee of their work.

I know when it comes to many cities there are long permit processes and also there are specific air laws that go into each city.I would love to hear a story that goes over an experience pertaining to developing/rehabbing a property in the DC area. 

Anyone have any good referrals for any of these sources that are geared toward or accommodate investors?

We take care of the entire process—from sourcing and purchasing properties to managing renovations and the final sale or rental.

As for offering subject-to financing, this is something that can be advertised under 'seller financing' in our local MLS, and there's investors that search specifically for listings with that marked, so that should introduce your property to a new set of buyers that may not have considered it before.

If you want off market deals, typically the best deals are the ones you are going to source on your own, not from an agent or wholesaler.