I have used ISTA straight from BMW. You can go to BMW Group's Technical Information System and pay for a 24hr, month, or annual subscription. If you are going to work on BMW's frequently, I highly recommend using this straight from the dealer rather than some potentially pirated copy. It is extremely straight forward. You ensure your computer has certain requirements installed such as Java Runtime Environment, C++, and the programming data package. All of which are as easy as click and install. Then you click start from the webpage which downloads a launcher for ISTA. This will allow you to even write service history and other things to your BMW. Foxwell and Autel both are nice to get you started, but if you want an all in one tool that will not only diagnose the problem but also tell you step by step how to fix it, then ISTA is the only way. Simply go to
https://bmwtechinfo.bmwgroup.com/#/login and create your profile. It costs very little in comparison to any other option in most cases. 24hrs is $32 and to be frank, I don't have enough issues with my BMW to need more than 24hrs to fix anything on it. If you do ... then maybe consider fixing it up enough to sell it and get a new one. If you like buying them to fix up and resell then get the annual subscription and register your shop. Personally I've seen the Autel MaxiSys 908 Pro II in use, and it is a very good tool but is very very slow. Foxwell is also extremely slow. A laptop with an i7 or i9 processor 32gb ddr5 ram and gigabit ethernet is not slow at all. Either way, make sure you have an adequate power source for while you work on the car which I rarely see mentioned at all in these posts. Cheers!