Roberta,
We recently moved because of stairs. I hear ya! The last couple of weeks were a challenge. I could do the 15 steps, but was increasingly tired out.
In my case, an OT explained that a chair lift, though a viable option early on, may not be the ideal solution because if/when my core muscle strength were to diminish, it would not be safe or practical. We were in a condo with no option for renovations of any kind because of space design and due to structural walls being in the way of any such plans.
I am sorry you can't sell - have you considered renovations to meet future needs? We had also toyed with the idea of renting our previous condo and moving to a rental, but decided, in the end to sell and relocate nearer my family.
Not sorry we did that. i can use my scooter if necessary throughout the place and have the bathroom I need. I'm just exhausted (still) by the entire move - but not missing the stairs!