Pretty much your questions are answered on the pricing page Prices - CS-Cart Multi-Vendor On-Premises. On premisis means you get the code. You can choose between subscription which is annual costs but come with support or lifetime licence where you choose to let the code get behind and then buy upgrades later.
On the pricing page you can expand the full feature list to see what comes with it.
RE developement coming from a background of VBA and SQL with basic PHP I find the coding very hard to get my head around. Others seem to pick it up pretty quickly. You have to follow their model and standard statements don’t necessarily work. Following the schema, picking the right hooks is key see their developer manual Developer Guide — CS-Cart 4.18.x documentation.
I have since my post come to view that content management (outside of products) is a significant weaknesses. It is an attractive feature that vendors can create their own content, but:
- I previously mentioned that all web pages and all blogs appear on all domains without the ability to not show irrelevent pages/blogs on selected domains
- Because all content is duplicated on each Domain it is not unique. Google highly rates unique user centric content.
- All hang vendor pages and blogs hang off of the marketplace root, not each vendor i.e. all content is here www.mydomain.com/all-vendor-content-root when it should be here www.mydomain.com/vendor1-store/vendor-content. Lack of structure isn’t good for anyone including search results. (each vendor can build their own structure under the root though)
The other thing to be aware of is there seems to be less effort on adding new features (see 89% decline in new features in each release from 4.13.1 to 4.18.1 - #4 by chickentwisty)