We have a 2400 sq ft laundry. Similar situation as TDL. It was a salon that was originally built to be a laundromat. Since the utilities were already in place, there was a significant savings to make it into a laundry as was originally intended when constructed.
We ended up building a Dexter laundry and installed used dryers and some washers that we acquired from a laundry that was closing an hour away. Our location was tucked in between many many older apartments. It ended up being a strong location and I'm glad we did it, but I am far from an expert... I only have one experience. Looking back, I would have bought all new equipment for the reason that all of it would be on dexterlive when only our new machines are otherwise compatible.
The machines are much more reliable than car wash equipment in general, so used isn't a bad idea... But for us, if we would have known the strength of the location ahead of time, we would have been better off buying new simply for not having to deal with other small repairs as often.
Hard mount is just like Mep assumed... Firmly mounted to thick concrete with very serious anchors (epoxied in even) so that the machine will not vibrate during extraction cycle. Soft mount are like home models that just sit in place and use a 'suspension' system to absorb the shock. The technology of soft mounts have come a long ways over the years, but it still means more moving parts to wear out vs a strong main bearing and a strong frame that just stays put. The only advise I have, is the crappier the place, the better your laundromat will do. I wouldn't look at if there's not one to compete with, as much as if the place is just generally in a low rent and populous area. Also, if you have transient workers (ie. oilfield), that can be incredibly helpful for customer generation and fluff/fold service. Also, don't discount how much a large washer will make. Having several of the largest machines in town is a big draw and is a time money/saver for the customer and end up making the majority of the business. We didn't even do any top load machines, and I think I'm glad we didn't... All stainless steel washers and dryers make a nice looking place.
Lastly, I would reconsider going cashless... Its very heavy cash vs
credit card since the customer demographic is pretty much low income only.