I like that they were upfront and honest with you. I would take them on as clients based on personalitiy and honestly, but you have to decide if you are ok with the late. I don't think it will take long to toilet train, and you'll probably look awesome and get all the glory for it. If you're ok with the lates you can give them a healthy late fee and at least make it worth your while. It's so hard to find honest clients these days.