New property to invest using $400k as down payment, loan of $900k -$1.3mil buy- assumptions.  20 units at $700 unit average rent or $168k minus debt of $50k debt and $60k expenses = $58k cash flow.  

If you take the interest deduction on your primary home the IRS will assume you live there and the fact that you didn't report it as an investment property, another assumed assumption they will make.

I think there was an assumption that I was marketing myself when I was giving him advice. 

However, there is typically a 5-10% management fee assumption for 5+ units.

Does this assumption include renovating units as the tenants turnover?

I thought about it, but decided the money I'd be putting into the panels, even if financed, would be better spent acquiring another property.Solar panels have even caused some issues at closing with contract assumptions and terms etc.

You are correct in your assumptions.

I was under the same assumption for a secondary residence (10% DP), but was on a call with a credit union last week and came across a 0% DP option for secondary (Non-VA).

You are making assumptions that only people with bad credit who can't get bank financing would buy on terms or that greedy sellers looking for a sucker would sell on terms.

The general assumption for me anyway is that a single property will provide XX in income, XX in tax deductions, XX in mortgage paydown etc.