The only word of caution I have for you is that warranties for R&Ms aren't transferable and that also excludes you from taking advantage of it should you need to replace any of the Bosch components.
I've gone a bit cold on that one anyway. I would be prepared to pay anything near what he is asking, ESP since I'd need some expensive options to make it work.
That load 75 on eBay, what do you reckon is a fair price for it?
https://www.ebay.co.uk/itm/Riese-Muller-Load-75-e-cargo-bike-/274722080974?_trksid=p2349624.m46890.l49286