Welcome to YT.
Sounds like you are really doing your homework. Yorkies do like attention. If your mom will be home then he should be fine. You can either baby gate him in a room (make sure it is puppy proofed) or in an expen. We have an expen for Hot Rod and the way I have it set up, it is about 4' x 8'. He has his crate, food, water and toys. We slowly opened up the downstairs as he got better at potty training and now after 7 mos he has the run of the downstairs minus 1 bedroom-which we don't even go into (ha, ha). That's there all of my houseplants have been banished to, to make sure he doesn't eat them. And yes, you may want to consider a companion down the road. Good luck with your search and choice.
p.s. I would probably do the same type of training with a larger dog as well.