Is this a safe app to buy and sell off of? I want to sell something and someone private messaged me saying to email them I did and they then asked for my address saying they'd express ship a check to me and have someone pick up what I'm selling and then pay an extra 50 for me holding the item. I'm quite trusting but I answered that I didn't feel safe giving out my address and asked if they had chase quick pay or if not if they could mail the check to my husbands work address and then ide ship the package myself at fed ex and cover the cost of express shipping. Anyways I just downloaded this app is it safe?