The lease & deposit is attached to the property, not the individual tenants. 

Congratulations for all your hard work.    19 units is a major accomplishment as an individual owner.    

If you have a well-maintained unit in a decent area, your tenants will want to stay, even if the increase is substantial and it is within market rent.BTW, prior to purchasing, ask the owner for copies of the most recent utility bills, tenant estoppel certificates (signed paper from tenant stating financial terms of the lease) and CLUE report ( A report that lists if any insurance claims have been filed against the property in the last 7 years) to ensure property is insurable.

My husband has been reading a lot about financial "freedom" and one topic that got his eye was Real Estate Investing.  

Hello All,In the past I have had issues with tenants applying to live in the apartments as a single individual.

I just got financial information and since Jan 2016 the income is up and down several times.

Though I don't know your strategy or your financial situation so that's obviously your call. 

You should base the price on its current financials not pro forma.

I know a few such as financial terms, closing cost, home inspection and appliances.

Without getting into the whole spiel, about a year ago my business partner @Tommy Mejia and I decided that we wanted to become financially independent and decided RE would be the best way for us to reach this goal.