Minimal changes to effect common entrances, no major shifts in load bearing, easy plumbing changes for wherever the new kitchen would be... it's a lot of boxes to check. 

Look for properties with updated roofs, electrical, and plumbing.

The main issue is that to do the ADU you have to spend so much bringing other items up to code like electrical, plumbing, lighting (windows) and egress.

Instead of platforms like Angi, try building relationships directly with contractors, architects, and developers.

Quote from @Paul Gupta: Hi, in California, For jobs requiring a license, there was CSLB (contractor state licensing board) which would give either a General Contractor license, or specialty licenses by trade (~60 specialties such as concrete, welding tile, ) https://www.cslb.ca.gov/about_us/library/licensing_classific...My Q: does Maryland and DC area have similar requirements? 

@Alan Mills You mention contractors not keeping a time line , not General Contractor . 

Overcrowding can strain plumbing, electrical systems, and air conditioning, leading to expensive maintenance issues.

However, these properties generally have a lot of land improvements that qualify as well as certain portions of electrical, mechanical and plumbing that can qualify.

Take the effort to solicit contractor recommendations from multiple people.

Congratulations to your continued success.That said we would like some guidance on crafting a contract where we would partner with contractor to go in on a flip together.