I'm not clear if you are looking at two quads or one 8 unit apartment. They are valued differently. Quads use Comparative Market Analysis and apartments are based on Net Operating Income.
To really evaluate the deal for either method, we also need purchase price and terms.
Owner financing can be really sweet. If they financed 100% of the purchase price, for example, you would be crazy not to take the free $900/month.
So, let's just assume they want 20% down. (You may be able to go lower which would boost your returns.)
Cash out of pocket is $200Kx25% = $40K
Yearly Cash Flow is $900x12 = $10,800
Cash on Cash return is $10,800/$40,000 or 27%
If your numbers are right, I don't care about property valuation, that is a pretty good CoC return. In four years you've gotten back all your money and still own the asset. No brainer.
Sounds like this property is probably in a D area or is in bad shape. Make sure you’re considering the likely low rent growth, substantial vacancy and collection loss, and other issues that could arise. Make sure that your risk tolerance is in line with the risks associated with this property. If it is your first property, you may want to avoid the headaches associated with a D area property.