Senior cat constant issues

My 15 year old girl has been having what feels like nonstop health issues lately. The last 5 years she has had issues pop up about once a year, gradually increasing to every other month/monthly in the last year or so. She has thyroid issues, giant lump on neck, constant wheezing/sneezing, intermittent puking, lethargy. I have taken her to the vet with each new issue and several times for the vomiting only to go home after spending hundreds with no real answers or solution. This year alone I’ve spent almost $2k on vet visits for her with zero improvement or resolution to any of these problems.

The vet has not once suggested or discussed end of life care or questioned her quality of life as she’s still eating and quite vocal. I am emotionally and financially drained by the constant issues and I hate to admit but growing quite resentful. We treat the puking and that works for a week or two then back to puking and snotting literally everywhere. I’m honestly disgusted existing in my own home due to the constant phlegm and vomit. Most recently she has started urinating outside of the litterbox despite having multiple options, cleaned daily. She urinated inches from the box this morning. We are in the process of trying to sell our home and literally had new carpet installed today. Noticed the urinating issue this morning before the installers showed up. No clue if this has been ongoing and I just did not catch it as most of the house is carpet and she peed on the LVP floor. I feel fucking awful because I love her so much but I am genuinely so over it. I’m already so stressed about selling the house with her in her condition and now the urinating issue makes this seem absolutely impossible, especially after spending thousands to replace the carpet.

I will take her to the vet this week as I’m well aware the sudden urinating issues are likely due to an underlying health issue. I am just at a total loss for what to do for her and for my own sanity and mental health. The thought of her puking and pissing on this multi thousand dollar investment is horrifying and I have nowhere to put her to keep her off the carpet. No family nearby and no friends that would be willing or able to take her, especially with the urinating. The only thing I can think of is to keep her in the bathroom with pee pads down which is daunting given that we will be showing our house soon. I don’t even know how to go about finding care for a cat in her condition as no one wants cat piss all over their house and she has a habit of coming right into your face and sneezing all over you. Idk what to do and I literally hate myself for being so annoyed with her as I’ve had her for my entire adult life and her whole life. I never imagined feeling this way about her and I feel like a total piece of shit. Waiting to sell my house isn’t an option especially since i just dropped big $ to replace the flooring specifically to help it sell.