How much is too much interest?

[Tim Emery]

How much is too much interest? 

I'm looking at an opportunity on a property that I want to buy. It looks like I can make $100k net profit if I put in $200k of my own money. But, if I put in 10% of my own money I can make $50k net. 

The rub is, I'll be paying 4 pts. and 20% interest on the 90%. Yes, I still should make the $50k net.  

This is more of a learning post, then a I can do better terms post. 

If you respond please help people understand why this works.

P.S. It's a short term loan. 

Thanks,