Just so we are all on the same page Parma would be a B-Grade Neighborhood but Old Brooklyn is by no means a B-Grade Neighborhood.

looks like you no longer have this issue.But in the future if it happens again what's been mentioned so far - screen the new tenant, fill out application form, collect app fee, and have all existing tenant sign.IN ADDITION, make sure the existing tenants and new tenant understand, and include into the addendum if necessary, that all claims, damages and deposits are shared by all tenants from this day forward.That means if you see a broken window and need to charge them for repairs tenant C can't say oh it's broken before I moved in.Or if tenant B moves out and six months later you charge a deduction in the security deposit on a hole in the wall behind the couch he says the hole wasn't there when he moved out so it's not coming out of his deposit.At the end of the lease when you refund the deposit it will be a check to "A B and C" jointly regardless of who might be there or not at the end of the lease. 

There have been a variety of strategies offered up and discussed in great detail on BP threads and forums, mine included, with regards to the strategy one would employ investing in A/B class properties versus C/D class properties, or TK vs DIY, 1% vs COC returns vs IRR vs ROI, etc etc, I think the most important thing I've learned is that each investor should define their goals, financial situation, risk aversion, willingness to be hands on, etc and identify what the best strategy is for them to meet those goals, and DO YOUR DUE DILIGENCE, and NEVER WAIVER on your metrics of evaluation.

Also, take into account the amended rules AB 2299 and SB 1069, and explore the opportunities they could provide you in the neighborhoods you are concentrating on.  

Comps for a B/C areas will be retail sales from owner occupants.

Title Commitment needs to be run on the AB, and then also on the BC showing B as the owner of record, before B is actually the owner.

I think you will be overwhelmed if you do not have a solid grasp of what you are looking for.It sounds like you are looking for a B or C class building so that you would have the opportunity to do some value-add.Are you looking for office buildings, retail, etc?

Cali government has nothing better to do than mess w/landlords, instead of stop spending on a high speed rail....(imho):https://caanet.org/assembly-bill-would-require-tra..."Under the bill, landlords and property mana...

Investing is all relative...for example, I'll take a B-class property that breaks even every month over a C-Class property that cash flows $600/mo. because it works better for my plan and style...the point is that any rules about returns are crap. 

I got into these duplexes because the cash flow was close to 2% which is great for a B- area in my opinion.