Please quote for this portion, if you chosen there are a lot more mods required, its not required you know prestacart.
This is for a retailer, that wants sites to SEO to each city.
I would use a common database for the product, from a master shop.
A user might be in ([url removed, login to view]) or ([url removed, login to view]) and make their product selection, as they go to https I want that the cookie data etc.. is transferred TRANSPARENTLY to ([url removed, login to view]) and can proceed with checkout. This is partly due to cost of secure certs for each site, that I want to avoid and also for easy administration.
If your not understanding or have suggestions or comments, feel free to PM me. If you have done this before, for gods sake give me the links to see it :)
centos,php5,mysql, let me know if budget is not enough