The lower class buildings look higher cashflow on paper but real life it all nets out around the same.

Take the lower of the 2 if it gets you the funds needed for the next deal. 

If you have 20% equity, you may also be able to remove your mortgage insurance and lower your monthly payment in the process.

Sometimes, the unsophisticated purchasers have to be taken by the hand by the listing agent and sometimes dragged across the finish line with a lot of services involved and typically a lower commission than a multifamily investment.

:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+ (roughly 5% probability of default), zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680 (around 10% probability of default), some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

Bankers are not allowed to charge points on traditional loans so you save money in closing costs and end up with a lower rate.

If the buyer has good credit, you might go lower, while buyers with poor credit might justify a rate closer to 9% or 10%.Market-Based Adjustments: Keep in mind the current prevailing mortgage rates (which are currently around 6-7% for traditional financing) and adjust accordingly to stay competitive while still reflecting the added flexibility of seller financing.3.

I have been offered to invest as LP in multifamily apartment deal.Underwriting is supposedly conservative and based on current cap rate (4.5%) and interest rate (7%) so if interest rates go down (which may as Fed has already started cutting rates), returns can be better than the projected ones as can have more buyers for Class A property in few years with lower mortgage rates.

And even with all those updates I am at least 20% lower on ADRs than 2 years ago. 

You bought it as a primary and kept it to start investing, but that doesn't sound like a good investment and HOA can keep going up or there can be assessments and your appreciation is much lower in a condo than a single-family.