Re: Building a retail store?

@nadifb I am assuming you don't own "Get to Work" (expansion pack)? If you do own it there is still some information (especially at these links) that should address some of the issues you are frustrated with...

There are no retail stores in-game unless you own "Get to Work". When you purchase Get to Work there's a world, "Magnolia Promenade". In that town you will find 3 pre-made, functioning stores. You can edit them or make your own. 
http://www.carls-sims-4-guide.com/expansionpacks/gettowork/retail/
http://www.carls-sims-4-guide.com/expansionpacks/gettowork/

If you own "Get to Work", you need to add the register somewhere on the lot, but the items in that lot are for sale have to be designated for sale in live mode by a sim who owns the store before it works properly. They can then sell the store and the game should run the store and your sims can visit/purchase from it.