Gross rent per month is usually the only figure that's calculated as a percentage of purchase price (to firstly see if it meets your investing criteria eg. 1% or 2% "rules"), whereas all expenses are then (usually) worked out as a percentage of rent - not purchase price (eg. the "50% rule")!

That's the type of real estate investing I have decided to pursue, I understand there are others and that I should not rule anything out but one thing I have learned in my career is, if you focus on one particular thing, you become and expert at it. p.s. sorry in advance if my introduction is wordy.

We screen, including calling vet, charge a pet deposit and have rules in the lease about maintaining dog damage, flea/tick meds, and no disturbing the neighbors with barking.

As a general rule you should use an S-Corp for everyday business (flips) because of the tax advantage of the salary dividend split.  

Multiple properties can eventually support your plan of cash flow being used to buy more properties.In the meantime, you can look for partners.  

When it comes to refinancing, do the same rules apply to qualify as far as providing tax documentation and pay stubs ?

Also have you read through the condo associations rules and checked to make sure there is not a large assessment coming or that the condo association is having financial trouble?

The tenant may voluntarily agree to leave in exchange for a cash payment or some other benefit, but you cannot make her leave unless you were completely removing the building from the rental market under the Ellis Act (and I am not as familiar with those rules to know whether it would work here).So, with all of that said, if the deal depends on this tenant vacating the apartment (which, if she is paying $350/month rent, it probably does), then I would only move forward if the seller will agree to deliver the unit vacant at close of escrow, OR, if you can obtain a signed agreement with the tenant to move out for payment (and for that agreement to be upheld, the tenant should probably be represented by a lawyer).  

Bottomline is find deals that aren't on the market yet and have solid documents ready to be able to support the offer. 

Folloe the 2% rule which I love!