First of all, it's hard to trust anyone or any agents. So just research deeply. Sadly my country doesn't allow foreigners to buy land directly. The only way is to take a business license and Registrar of Joint Stock Companies. This means you have to open a company here, no matter small. Then you can buy property here legally belonging to the company name and you can sell it at any time you want. Since you don't want to buy sell and going to earn from rent, then there wouldn't much issue and you may do it without hassle. It doesn't cost much though.
Thank you for your advice. Setting up a company and hold stock share with agent is also fine, because in some parts of the world, it could be possible that company ownership right is as strong as land ownership right (but not in my country).
Still, I'm willing to pay for some agent if he can write formal papers in esoteric foreign language instead of me though.