Buying from home is probably fairly safe. The biggest disadvantage is that if you do not use a bridge or something, your ISP can tell that you are using Tor. That could be a problem for vendors, especially vendors in less densely populated areas. Short of that, working from home is possible to do securely, but if you are hacked or your Tor circuit is compromised the feds will identify you, whereas if you are working from random WiFi they will only identify the location you connected from. So it is definitely safer to not use your own internet connection, but it will only matter if Tor / Tor Browser have a security failure, or you are otherwise infected with malware somehow. I would argue that it is even somewhat safer to use a neighbors WiFi than your own internet, although this is only for two specific reasons. The feds can trace live WiFi but if they don't trace a connection while it is live there is a good chance that they will never be able to determine that you were using the open WiFi for the session they are interested in, if you spoof your MAC address then it is even less likely. So if you live in apartments or move around a lot having only used other peoples WiFi can actually give you great unlinkability after you move, if you have not been traced yet there is a very low chance that you will be traced in the future, even if there are logs leading up to the WiFi access point and LE eventually work their way to it. The other situation where it can help is if you screw up somehow and realize that you screwed up, perhaps you accidentally didn't use Tor for something sensitive or something. If you realize that this has happened on someone elses WiFi you can immediately stop using it and still have pretty decent security so long as you take some countermeasures, if this happens while you are on your own internet you are much more likely to be fucked. It is worth noting that if you are rooted even if you are using WiFi there is a good chance you will be fucked, I am not sure the accuracy of WiFi Positioning Systems these days but I imagine if the feds can gain remote control of your WiFi card that they can remotely geoposition you accurately enough to determine who you are, though in apartments that share walls they might not be able to differentiate between you and your neighbors.