The advantage of investing in a franchise in a popular established business, is that it's already popular and established. You don't have to work so hard to build a customer base.
The disadvantage is that you have little to no control on how the business is run. All the way down to how many slices of pepperoni go onto the pizza is already determined for you and you must follow the franchise rules.
Last I heard, a decent USED pizza oven was running about 5 grand. Add to that, all the furnishings, kitchen appliances/utensils, payroll, insurance, property lease, utilities, business licenses, advertising, taxes, the purchase of product and supplies, uniforms/aprons, and I'm sure there are many things I'm leaving out.
The County Health Department where I live requires 3 stainless steel sinks for dishwashing and an additional sink in the kitchen for staff to wash their hands. (Not counting the one in the restrooms.) A certain type of flooring, oven hood has to meet size and standard. These are just some examples.
The City requires a certain minimum # of parking spaces that are adequately lighted among other requirements that most people don't take into consideration before leasing a property.
Starting a new business is expensive and I would recommend a person starting in any restaraunt business have at least $150,000 plus a prudent reserve (3 months operating expenses). You have to be able to get through the first year which is not going to be profit making.