Costs is definitely something to consider. You're basically looking at spending double the amount you are now. I don't owner two big dogs but I know that whenever I fostered a senior beagle it threw everything out of wack for a little while. The senior girl wasn't trained at all and would growl at Hallie over the bed and me. She was a good girl though we didn't get to keep her though, we fostered a younger beagle mix and that went very well. She was potty trained and trained in every other aspect and got along with the family and Hallie and Peanut. I wish we could've kept her but we couldn't afford another dog and we were getting illegal (only 4 pets allowed in the city). I think it depends on the dog. You could keep her for a trial period though you would probably get attached. It sounds like she'd be fine with your other dog and everything not to mention you have experience already in the breed I say if you can afford it then go for it! She needs a home 
