Need some planning advice

Hi guys. Im planning a new project for a client. and they need the following requirements:
1. a website thats members only - a monthly paid subscription is required.
2. one section of website sell merchandise on the website (physically shipped)
3. 4 sections spit as categories selling photos (digital download)

Note. The monthly subscription may be based on different pricing plans (so may consist of a price per month, or every 6 months or yearly price plan) - Im thinking for this using a seperate payment system with a selection of different paypal subscription buttons.

Then I need to work out an idea for above points 2 and 3 so that would consist of a cart system. perhaps somehow have 2 seperate cart systems or have 1 cart system but perhaps detects if an item is a physically shipped item in which case prompts user for additional payment options (delivery option and address details).

What advice I am looking for on here, is a logical approach. I think it would be logical to seperate the website membership payment system from the payment system used for selling digital downloads/physical goods....im just wondering the best method for the later...since if a user is purchasing digital downloadable photos they wouldnt need the checkout process where it would ask for a shipping address as the digital download would be stored in their membership account...also if they did order physical goods then the order summary would be stored in their membership account.

any thoughts or advice would be greatly appreciated at this point :)

Chris