Steam Loco questions froma noob

I am looking to add an affordable steam-type loco to my ho train/slot car mix layout that my grandkids and I love to play with. My track radius is 18". What would be a good, inexpensive loco to buy? I want to pull 5 or 6 cars and have a small incline to climb. 0-4-0? 0-6-0? 2-6-0? Any brands to avoid? Any help is much appreciated. Thanks.