@Shoshana Shulman - I would be very very wary of sinking every last cent of my available cash into a C+ property in a different country. You have zero wiggle room when something goes sideways - and it will eventually. (Not sure if that $500 cash flow includes allowances for cap-ex- but I hope it does.)
A few comments on your post:
"For that investment of 68,000 dollars, I have half of it in cash, and the other half would have to be a loan. I would earn 500 dollars for that half as well, so now I would be earning 1000, after all expenses, instead of 500."- That's theoretically before debt servicing on the 50% financing- so your cash flow will in effect be less than $1000
"I would consider hard money lending, but I need to be 100% sure that my money is guaranteed"- From my experience- there is no such thing as 100% guarantee on HML. Its a high risk business in any event and all the more so for a foreigner without very deep pockets, local knowledge and experience in expensive and time consuming foreclosure procedures.
In short - my advice would be to stay with the current partner (or look for someone else acceptable to buy him out), continue enjoying the $500 current cash flow and look for alternative and diversified places to put your other hard earned capital.