I have purchased an off-market property from an investor who now wants to sell the rest of his portfolio.

If you want to combine two or more lesser sales into one higher purchase that is fine as long as your purchase meets the timing requirements for each sale.  

It is 100% the buyer's / investor's responsibility to do Solid Due Diligence before purchase. 

The only information I had to go on was with the last Lender informed me so maybe it was specific to the company they were with.

Most of our loans are fully amortized and those that aren't, are 10 year balloons where we'll have more than 50% equity (at the purchase price) upon loan maturity in 2030+. 

Mortgage lenders will qualify you for a higher purchase amount for multis than they would on a single, because they will count the rent you will be making on the other units as additional qualifying income for your loan application.

Can you please provide a specific example - there is no rule against this, and you are certainly allowed to.

I had a friend purchase a Vacation home financed with RBC last year. 

Purchase price: $232,000 Cash invested: $18,000 My real estate investment journey began with a leap of faith when I purchased my first investment property—a charming but very needy fixer-upper in Connecticut.

So you wouldn’t get any depreciation on your new purchase assuming you only spent the $450k.