When are you too over levaged?

[Brandon Duff]

Ground work:

Purchases: 

2015 SFH1 purchased 3/2 118k rents for 1100

2016 SFH2 purchased 3/2 122 rents for 1100

2017 (10/28/2017) closed on first multifamily (4plex) for 268k 12k in repairs expected rent per unit is 800 but looks closer to 900.  2/1 

Used 40k from refinance from SFH1 to use towards part of the Down payment for the multi family. 

SFH1 debt is 129k worth 172k 

Mortgage is 700 now

Rents for 1100

SFH2 debt is 96k and worth 160-170

Mortgage is 638

Rents for 1100

MF1 debt is 201k with 300k

Mortgage 1500

Rents for 3200-3600

My question: 

I currently own my own training company it is just me. 

At what point do you start paying off debt or stop buying properties.. like how many mortgages do you feel is easy to handle feel you won't over leverage.