I grew up sailing scows and other small boats. Sailed with a few guys out of Milwaukee and Port Washington on Keel boats.
The first time I chartered was in Bayfield at the Apostle Island, great place to go. All I had for them was a resume of a bunch of sailing. I did not have ASA certification. They never even went out on the boat to check me out to see if I knew port from starboard. Had a 30' boat for 4 days. Next year we went to a different charter company and got a 45' boat for charter in the same area. No one check me out, just sign the check. I have since been to the Caribbean twice and chartered with Footloose a Beneteau 473. they didn't check me out either.
I would recommend to take your lessons with Milwaukee Community Sailing Center. I would also show up at South Shore or Milwuakee Yacht Clubs on their race days and find some larger boats to get on. Try to get into a few across the Lake races. It looks good on your resume. You will get more experience on the water than just doing a week class at ASA and make a lot of friends. If you want to take some certification classes locally, check out Performance Yachts, I know they do some.