Our 10 year old female chihuahua is completely housebroken, but the last 3 days she has urinated 1 time each day in the other room. She goes to the vet once a year for her checkup & shots but is not quite due yet. Her normal routine when needing to go outside is to get down from her pillow on the couch & look at one of us and shake her head making her tag on her collar rattle. Then we always take her right outside. I'm unsure of what may be going on. Money is seriously tight this month with kids going back to school & bills, & we also had to take our box turtle to an exotic animal vet that charged us $150.00 just for the visit. We aren't noticing anything unusual going on with her, & nothing in our home has changed (i.e. not being home for long periods, etc). She hasn't let us know she needs to go outside, when we've all been in the room with her. We did use vinegar & water scrubbing the areas thoroughly. She's let us know several times each day out of the 3 days this has happened when she needs to go out & has gone potty without any problems. Any idea what could be wrong?

She may have a UTI. She may be getting old enough to not be able to hold it in. She may not like the weather out. She may have gone there when you didn't notice her just once, and her need is more urgent as she ages. She may have had one accident and now the scent is attracting her back to that spot or room anyway (that happens with my Jack Russell).
Close off that room and hope, and keep an eye on her.
After cleaning a spot, I pour something really strong smelling on it, like cheap cologne or after shave.

I understand money being tight this time of year, I swear that back to school is even worse financially than Christmas time, for me I add two birthdays right before school as well.

Having said that, I really do think you should have her checked to rule out anything medical. If this is a UTI, which is very possible, the sooner it's diagnosed and treated, the less it will cost in the long run, not only money wise, but health wise for your dog.

Is she acting any different? Sleeping more? Less active? Anything of that nature?