I want to start a Thrift Store in Simi Valley CA but am not sure where to start... I have all the product to put in it, Selected a name, and found a location, now what? Do I need a business license and how do I go about getting one.

Will this be a long process to get one up and running does anyone know?

It shouldn't take too long, maybe a month, for a thrift store (no food or other special licenses required). First step is your city hall, where you get a permit for that type of business at that specific address, so that they can decide if there is enough parking and the building meets codes. Try the zoning office or ask. Then you apply to your state for a business license. Google CA.gov. If you have no employees, you don't need to get an Employer Identification Number (EIN) from the feds and your state, you can use your SS number and pay taxes as yourself d/b/a your store name. If you feel all will go well, you can rent the location and start getting it ready. Someone at city hall probably will know how long it will take.