One of the tenant insist they have legal right stay there as M2M tenant ( still enjoy paying $300/mo below market rate) because it is legal 4 families and landlord can't ask them move out even owner occupied or landlord family move in as reason to ask them move out.Please BP nation help us on the situation to deal with the problematic tenant.  

They want retail price for their houses and have a plan to sell  2-4 annually on the MLS.As they won't owner finance and I can't offer any more, do you know of any more advanced techniques that would allow me to pay a higher price for the properties but still have reasonable cashflow?

This is a good reason to only do month to month leases.

Cash flow positive is still great no matter what way you look at it and if you don't have a specific reason other than the cash flow thing for wanting to sell ex. say no longer an area you want to own the investment in or in the next couple years you could see no longer being cash flow positive because of HOA fees/Taxes etc I would hold onto it personally as a positive asset.

,There are many reasons they may not respond.

When I asked them about getting on the lease, they both admitted to an unacceptable criminal record, but for various reasons believed they were entitled to stay.

Is there someone that could create everything for me at a more reasonable price?

Not even so much as you getting sued or losing your license, one of the reasons you get the portion of your commission is the work you do in bringing listings to the home office, along with showing properties, walking buyers/sellers through the process, etc. 

They are right, you can't block the stairs for code reasons. 

The high rents in Baltimore are not economically reasonable.