Start by reading THIS:Edit: I just did some further reading
As far as I can gather the Luxor Solo was an Arta Guban horn.
I suggest you do a little research, I hesitate to make any suggestion.
That is about the size of it. Starting sax repair, even for someone who has dabbled in brass repair...there is a learning curve there, and a time investment. If you are in no hurry to really start playing and are OK with trial and error learning to do some sax work, then heck, buy the Keilwerth 3 ! BUT if what you want is to get playing, then do what you can to buy a horn which is playable. There will be other days in you sax future where you can start to hunt for potential refurbish/repair candidates. Doing that with your first horn is probably not the best way to start....you might see cheap saxes because the owners don't want to spend any more money on getting them fixed. Although you've done good work on a trumpet, a sax is a completely different instrument. More complicated. Yes, you could eventually learn to repair a sax. But it's very different from a trumpet.
One problem is that - as a beginner - you won't be able to assess the condition and 'playability' very well.. If you don't know any experienced sax players, perhaps you could hire someone a sax teacher) to go with you. He or she would be able to give you advice. Whether the sax is worth the money. And what needs to be done to get it playing as it should.
I realise your budget limitations. That's why I think that when you buy your first sax, a more experienced player should advise you on either "yes, it's worth the money and plays OK" or "yes, it's it's worth the money but this needs to be fixed and will cost roughly x euro'" or 'no, for the same money you can get a better sax than this one".
Up to you. If you're willing to take the risk, just go for it. If it was me, I'd want to know that my money was well-spent.