Hi there!
I can done it with writing several classes (dvd, client, client_monthlypaid, client_dvdpaid, bill, store etc), with best clearance of you task specifications.
The real price is 75 USD, but i can not do a bid lower then your project minimum, you know.
The 20 task points you've mentioned requires basic preliminary architecture (or anything will look lame). I've drawn one, and it puts pluses over all 20 points like this:
1. yes, for dvd and client
2. yes, for dvd and client
3. yes, for dvd
4. yes, it's just a good programming style; you will have app. 16 files
5. yes, with bill and client
6. yes, with client
7. yes, with dvd
8. yes, with client and/or store
9. yes, all classes
10. yes, for dvd, for example
11. yes, with client and store
12. yes
13. ok, with dvd
14. yes, with store
15. yes, with dvd
16. yes, with bill
17. yes, with store or client
18. yes, with client
19. yes, with client
20. yes, with client