In this case I think asking for a fixed fee (rent) from the trainer might be a better choice. Of course everything is negotiable and talking to him/her would be great way of see what he/she is willing to give up in order to train at your location (assuming this is why you are asking this question). This way the trainer can keep charging his/her rates and not feeling like giving up a big part of his/her income. I hope this helps.
BTW, that is a great last name!