If you don't like the area you will most likely not like ANY tenants. You will not be happy then being an owner/landlord. I really do not recommend that you start your landlording career with such parameters. Find a better object, maybe a Condo (or two, whatever you can afford) where some things are taken care of. Yes, less cash flow but typically also less hassle.
Re your questions:
#1 Yes and yes. Consult the leases. You can always get rid of tenants under the rules dictated by the lease and/or law. Doesn't mean it's going to be easy. ;-)
#2 Seems a bit high but not totally unreasonable, but then again I never checked the Costa Mesa area for that.
#3 Good question, actually never had to do that as it was either handled by the HOA fees and/or the tenants paying it. Would be curious myself to hear an answer to that.
#4 I would factor in property management, even if you plan on managing yourself. You should also make sure you have sufficient funds at hand. You have 1 building but you have 4 units. That's 4x potential problems (water heater, hvac, appliances...). Budget for it. Imagine you have 2 water heaters going bust (literally) and the HVAC dying in one unit, and a burst pipe in another one and water damage in the unit below. All that within one month. You need serious money to cover these expenses! Doomsday scenario? Maybe. Totally unlikely? Definitely not! Budget for it. You can't leave the place unfixed for x months till you got the money to fix it...
#5 Run with the usual figures but consider the buildling's age and overall condition, of course. I don't really - generally - budget differently for a 4-plex than for say a Condo. Although typically with a Condo the roof, for instance, is usually the HOA's problem. With a 4-plex it's definitely yours.