Is Multisite the answer to shipping and payment issues?

I have been reading about this all day trying to decide what to do. I have multiple marketpress related problems that I’m thinking may be solved by using multisite.

First of all I don’t understand the difference between multisite and wordpress MU. From what I understand multisite is something that’s built into the core of wordpress and wordpress MU is a plug in from WPMU. Or am I wrong. If so which one should I use if any?

Here are my problems (site=

First – your new shipping modules are awesome; however is still have this basic problem. Different growers and artists with vastly different products and shipping needs will be selling their stuff on my site. If I go to multisite am I correct that they would be able to have their own settings for shipping on a per site basis?

I have not figured out “configured” shipping yet. If I check priority and first class in the options would it just be up to the customer to choose the correct shipping? Can I make it so Priority is required for certain purchases – like plants? This is what I started off with working on today and I think this will be a separate set of questions, but I wasn’t able to get the configured option working yet.

Is there any way to have different settings on a per product basis? I’m thinking the only way is to give those really “unusual products” that have different shipping needs their own store.

For example: Assuming that I have multisite and one of my customers has their own store. Say they sell lip balm, cards and plants. Lip balm and cards could be mailed together, but plants will be mailed in spring on a different date. Should the plants have their own store? In other words this person would have 2 stores?

Second – I’d like to use chained payments. Is that available on a regular wordpress install or do I need multisite for that. I read that chained payments were not available with the global shopping cart. Would this mean that a customer would have to check out separately from each store on my site?

Would each store be able to use different themes?

If I used a multisite install with stores that have different domains vs. stores that have different paths would one choice be better than the other for solving the above problems? Which one should I choose? I’m leaning towards a “path” style install.

It is not clear to me if a person needs to purchase different domain names for the different stores?

The large majority of my potential users are not at all computer savvy. This means that I will probably have to do almost everything for them. This is why I have not used multisite before. Right now each person just has a static wordpress page and product pages and I pay them the old fashioned way with a check. This will of course become problematic as we grow.

One more thing about chained payments, I will go to paypal and read more about that before acting, but do you know if pay pal charges you twice; once when the customer pays you and once when you pay the store owner? Or is it one charge?

Maybe I’m missing the boat entirely and there is a better way to solve these problems. I’d love to hear any suggestions you may have.