For instance if this is a $10M portfolio that's levered with loans totaling $9.1M, there's no equity that can be pulled but if this is a $1M portfolio with $100K of debt, its a different story.

For context, I will be assuming his VA loan at 5.1% and he will be doing seller financing for the remaining equity and sale price. 

I've helped people with SBA loans to purchase real estate for a business, but for buying rental real estate, the DSCR loan is a much better option.

The other route you can look into is purchase+rehab loans if it's going to be a primary, if it's an investment then using hard money, bridge loan, or DSCR.

Is there a pre existing loan with that bank with either of you?

One thing I continue to think about is how valuable 2-4 unit properties are becoming, and will continue to be, since Fannie/Freddie took the income restrictions from the 5% down conventional loan option for house hackers. 

We were able to get into it with a 5% down primary residence loan.

Quote from @Vince Scipione: Standard would be an FHA loan for your situation more than likely.

I've also used traditional loans through regional banks and a few SBA loans. 

So there are a million realtors, loan originators, accountants (RE is, for most, not complex vs other small business.)