If the DEF system is what you have a problem with, Xentry OpenShell with a cloned C5/C6 or Xentry PassThru with Scanmatic 2 Pro will be the cheapest ($500) option to go with. None of the above mentioned scanners will help you with DEF system, none of them are capable of doing SCN coding.
The cheapest Autell that is capable of doing SCN coding is the one from the link below and it requires a subscription on top the cost of the tablet itself with the j2534 passthru module.
https://www.jbtools.com/autel-maxis...MI7tSopbvS6wIV8IFaBR0lBQHhEAQYASABEgJJQvD_BwE
Xentry does have the capability to SCN code and it does require a subscription also, but the difference is that there are plenty of places where you can buy a "one time SCN coding" access for $25. AliExpress is a good source for buying that.
Also... If you buy a laptop or hard drive with Xentry that will have Vediamo software on it, you can get a seed key calculator for Vediamo and with that you can unlock the ECU for clearing or resetting the "0 start" or "start not possible" without SCN coding, and you can do it as many times as you need to... Let's say you have a bad NOx sensor that triggers the start count down and limp mode, and you can't really fix that right away, with vediamo you can clear and reset the start countdown as many times as you want, and continue driving that van until you have time and money to fix it. So the flexibility that you will have no other scanner will give you...