OP, I have been down this road. One of our getto houses in KW has a walkout that was "joe contractor done" , I had one put in my previous home and researched doing one here coming in through garage floor. The garage floor was not down, it had a ton of gas vapour / exhaust issues that ruled it not feasible. The getto KW house had a badly done drain, and you NEED a drain, even with an awning, blowing snow can fill the hole, then it melts. We had to dig the drain out and reconfigure it. It was 2K to fix the bad drain when done. The one in my previous house had a concrete block basement and cutting to put in the door was simple and minimal. Cutting through a 10" poured foundation is not cheap. ANY contractor that tells you a drain is not required is not capable of doing this work, without the job will not be to code. You may not be covered for flooding insurance and selling the property with a mickey mouse door could be a problem. Real contractors will pull permits and insist on doing it legit. Your home is most peoples largest investment, why do people even think these hacks with a pickup and a shovel are ok to talk to.