The important factor in increasing income is the number of doors you own not the number of buildings.As a side not having equity in a rental property decreases cash flow due to the opportunity value of cash.

At the beginning of January they inform me that household income has decreased and they won't be able to afford that particular property anymore and would like to know if I would have anything available April 1 in their new price range. 

If a shorter term gives you a considerably lower rate then you might better stomach the decrease in cash flow for the improved lifetime profitability.  

I see 2 options for you:1) Push to get the loans paid down (increase salary, decrease expenses, time to pay down) to improve your personal debt to income ratio2) Look at larger properties (commercial loans) where the lending criteria is based more on the property than on your personal numbers.

Right now I have to recalculate the numbers, because not only did we fill some vacancies, but the expenses decreased as well, which brought up the NOI even more.

In the course of one year a house typically won't increase or decrease materially.

It appears to me that your partner believes that the rehab budget should only be $20k--I don't believe he sees the same value for expenditures beyond that level or he wouldn't propose to decrease his contribution beyond that. 

Generally your rents increase and problems decrease the further west and north you go.  

Sanders will increase gov't spending in a depression, he's Keynesian.Clinton will decrease public spending in a depression, she's a neo-liberal.Trump, who knows.

We have been successful in adding value to these units, decreasing expenses and increasing cash flow.