The best you can do is risk it. Playing safe doesn't have the possibility of the best results. Just make sure you add people that don't have a private profile and inventory. Most of these people that want to be added may just want to have some people to slowly trust and get good deals from when the time comes. It can also be mutually beneficial. No one can hack you in steam unless you click a link they sent you. You want profits, learn to take a risk. And basic rule: Never click links in steam.