I lost both my parents within 90 days of each other about six years ago. I'd offer this.
If your mom wants to spend her last days in her own house, my recommendation is you do what you need to to make it happen. She spent a lifetime caring about you, your siblings (if you have them), grandchildren (again, if they're there), and the least you (or any of us, in a similar situation) can do is to make her last years the way she wants them to be.
We did this for my mom. After my Dad died, we didn't know what would happen. Well, all of her illnesses came to a head, and we (my four brothers and four sisters) had to make a decision - do we put her in a home, or give her what she wants, which is to be in her own home? We decided to give her what she wanted. We ended up doing a lot of work, lots of personal care (my sisters and my sister in law Rose are saints for that), but it was worth it. She got what she wanted, and went out in a place that was familiar and comfortable to her.
If buying the rancher and having your mom live with you will make her remaining years that more pleasant, I unhesitatingly say do it. As in my case, I think she's earned it.
My two cents,
Alan
(Message edited by ajdover on January 06, 2007)