We did that with our feral cat. We got him fixed and he is now a tame cat who wants to live inside. Our beagle does not like that idea at all. The dog has started peeing in the house again to show her displeasure at the cat coming inside. I do not know what to do the make her stop!
So, while everyone is giving liane 2010 advice, I could use some as well.

I brought a stray, spayed kitten into my household this fall with worries that my hyper Schipperke/Pom would try to kill her. I kept her isolated a few days in the bathroom with a collapsible gate between her and the dog. My dog showed lots of interest but nothing beyond that.
Once the cat learned to climb over the gate nothing happened between the two since she totally ignored my dog as he walked behind her sniffing. They now play chase with each other and sometimes sleep together on the dog bed or chair. They also wrestle together and I'm surprised by how gentle my dog is.
Even tho they get along so well, I still keep an eye on them when they're playing and she is shut up in a hallway/laundry/bath area of the house every night. She accepts this with no complaints since it's what I've done every night since she arrived. Of course, I place some toys and her 'tunnel' in there also.
I never leave them together in the house alone. Either the dog goes with me or I close the kitten up in her area.

My dog is very bonded to me and although I looked for a companion for him for a year I could never find another dog that I thought he'd accept and not be jealous of.
To me, it's ironic that the kitten ended up being the best companion I could find for him. She's not demanding of attention, she can easily get away from my dog when she wants by jumping on furniture and her tower, and my dog isn't threatened by her presence.

I suspect your dog will enjoy having the feral cat as company.
You'll find she's going to spend a lot of time getting comfortable in your home and there will be periods where the more you ignore her the better.

I think it's great that you're willing to give her a comfortable home, especially with winter coming on! Good luck and keep us posted!

lin01,

Sorry, I forgot to respond to your question! I would suspect something else is going on with your dog besides being upset with the cat. Have you had her vet checked to rule out bladder issues?
Beagles are a breed that can be difficult to housebreak so you may have go back to a basic housebreaking routine with her. Does she have a dog door?

Re; the beagle it could very well be that this is stress related as my dog has done this too, but just to be sure I would take a urine sample to the vet if it continues.

In terms of the feral cat I am considering, she is not a kitten anymore so she is more set in her ways if you will, however she is spayed so her wildness may be a bit tamed. Yesterday I saw her go across a street for the first time, usually only saw her in the yard so of course that gets me a bit anxious about cars, safety etc. Plus lots of meowing so I am wondering if she is distressed. How much does it cost to keep a cat? Never had a house cat let alone a feral. Again, my biggest concern is how it will affect my 14 yr old dog.

Do you have a room in your home that you can keep her in once you catch her? IMO you should keep her in one room so that she can adjust to your home, its smells and noises, and so your dog can become familiar with her.
Cost is relative. You'll need to buy a litterbox, some litter and then food will be the biggest cost. What is she eating now, and are you feeding her?

She could be meowing because she doesn't feel well, or she could be cold and hungry.
If you aren't able to catch her, at least set her up with a shelter, lots of straw/bedding, food & water.

I still doubt there will be problems with your dog as long as he doesn't corner her and try to attack. How does he act around her when he's outside?