Full Stop.The OP needs to cash flow and be proficient at screening and managing multiple units/properties.

Here I was cringing everytime it rained, but thinking I was gonna skate through unscathed....NOPELast night I got the phone call from my property manager...YEAH...UM...YOU NEED A ROOF...I knew it was marginal, and  I was hoping it would make it, but NAH.It's getting fixed today or tomorrow...Hopefully all the tenant rights advocates will praise me for my quick action!

I phone interviewed 6 of them. 

If possible we could maybe do a phone call or video chat that way you can explain everything to me for clarity. 

They did, and I gave them a brief phone call to see the unit (they were doing it FSBO).

Now the balance amount is huge .... he said he'll pay some amount this month and will get a document signed by notary to pay the remaining balance in a month. n we agreed to it too .. now he is not answering our phone calls...no reply to text / emails... what should we do now?

You can have credit cards, residence, phone lines, etc. for years with no lates or defaults but still no credit score.Unfortunately @Mike Lambert is correct that while there are Canadian banks that do provide loans for US investing, they come with significant limitations.

Set your screening standards and stick to them.

I sent them the contracts for the place after screening them, and after they stated on their application they had one "animal"--not "pet."

If you are putting the deal together and will act as the manager of the property (collecting rents, screening tenants, coordinating repairs, banking, accounting, etc) then you should deserve something for your time.