Purchasing Hot Water Equipment

Looking for some advise on what direction I should use regarding hot water equipment. I am currently in residential but taking the necessary steps to transition into commercial. I am debating on whether to purchase a hot box for my current 8gpm 3500 psi rig or just get a new washer with hot water attached already? 12V or 120v?

Make sure it has Beckett burner instead of Wayne. Wayne’s are hard to adjust.

I just bought this one, but ideally you should go with the 115v. Just speaking from a few weeks of research.