Use your common sense. Meet him first in a public setting, for some coffee and conversation. We are not talking about hiring for one hour, we are talking about a long term arrangement, with multiple hours meetings involved. You should make sure there is good chemistry. If you are not confident, go slow. Your safety is paramount.
Said that, you are not going to get much from a 7 days trial in SA. In my experience it takes a long time to comb away the bad weed, but there are very worthy guys in there. Check the series in my blog, you may find some useful tips there.
http://ilikepinga.com/2017/06/30/seeking-sickening-arrangement/
http://ilikepinga.com/2017/07/11/finding-arrangements/
http://ilikepinga.com/2017/07/21/finding-arrangement-2/
http://ilikepinga.com/2017/07/31/finding-arrangements-3/