I'm in the process of buying a small town diner and wanted to put together a bike trailer to get supplies (mainly groceries) with. I've been car free since early May. I do my weekly grocery shopping by bicycle obviously but until now never had the need for a trailer as everything I needed for the week fit on my rear rack and in a backpack. Shopping for a business means buying everything in bulk, something I wasn't keen on doing for myself and obviously my rack and backpack won't be large enough.
I was thinking of a custom built wagon of sorts, big enough to hold at least 60 pounds worth for up to 30 miles on a relatively flat path. How are trailers usually attached to the bike, via the seat post or the frame ? Any advice is appreciated.