While Pepsi may supply you with fountain equipment (and I’m not so sure with a 15 seat diningroom), you will be responsible for providing an ice machine. A top mount unit could be $2000. You probably have a floor mounted unit now, but don’t underestimate the pain in the ass of filling the fountain unit by hand. The fountain also needs a nearby floor drain with easy access (It will get clogged with syrup crap), electric and water supply. You will need a location in the BOH for the syrups in use, and to store backups.
foam cups are .06, and keep beverages colder an hour longer than paper cups. Pepsi will sell you paper cups with their logo for about .30.
while the cost difference is nice, foam cups take up 10x more storage space than paper cups, so keep that in mind when deciding.
Also, your Pepsi fountain will have only 6-10 drink selections, 1 of which has to be non-carbonated (usually lemonade). So you’ll get pepsi, diet, lemonade, dew?, rootbeer?, sierramist?. That leaves out new introductions, diet dew, caffiene free diet, and stuff like that. You can still offer those in cans, but now you are running two systems.
Finally, if Pepsi provides the fountain, they want only their products. So keep that in mind if you offer Dr Pepper.
Just some things to think about. Good luck