Health concerns

Question
I have a Sheltie mix that was given to me by a friend about 4 or 5 years ago.  Cozie was about 8 when I received her.  So she's going on about 12 or 13 years of age.  

She has always been a good dog.  One of the best.  But she has recently gone down hill fast.  She recently aquired a skin rash of some sort that has caused all the fur on her rump to leave.  Her skin has turned black, and she smells horrible. (Although I've bathed her again and again.)  She also is very dry and swollen around her mouth.  She is loosing fur around her eyes, and they are goopy and infected.  I think she has an ear infection, as she has fought those before and I'm seeing the signs again.  She has lumps on her rib cage and on the bottom of her tail.  I also think she's loosing control of her bladder, as I'm seeing a lot of little wet spots on the carpet.  (She is also doing a lot of licking down there.)  I'm at my wits end.  I've called vets and of course they all tell me, "We'll have to see her."  We are a VERY budgeted family, and although I love her to death, I can't afford to put hundreds of dollars into a dog that may give me another year of life.  I guess I'm looking for advice. Even though she doesn't look like she's in pain, (although I can tell she doesn't feel well.  She doesn't play, she just lays around and mopes), is this a worthy reason to put her down?  I was advised by the vets that skin problems are very costly to cure.  I just don't know what to do.  I love this dog.  And if it was just one or two conditions, I'd check into fixing her.  But with her age, am I fixing her only to have her crash and burn again in a few months???

I guess I'm just looking for someone to tell me it's time to put her down.

Thanks for your time.

Answer
Thanks for your question.  I cant tell you to put her down.  However;  without seeing her or her condition then I cant tell you what is wrong with her.  When you notice that she is stopping doing the things that she loves like playing ball going on walks and other things that you know that she loves then you will know that it is time.  She will let you know when its time and you will know in your heart that you did the right thing because she was not herself anymore.  When little things start disappearing and she is not herself then its time.  Just dont let her suffer.  Hope this helps.  Keep me informed.

Kati