What’s the cost of bundling? 18 inch rims

Hello guys. Spring is already there,and I absolutely have to buy rims,so I can put summer tires on it. It should be already 18 inches (18x 8 )-better Proline PI -,but always stands in the report to bulge in front and back,or to extend wheelhouse interior wings etc. Unfortunately, don’t know me about it.Did I look at 17 inches,but I like them,there is also the one to bulge and to adapt artificial parts.Do you know about it????What costs to have bulging???First of all, who does something like that??? Or does anyone else come around there? Thanks and greetings…..