Valencia CF is planning on selling Goncalo Guedes and the club would save something like 5 million a year on wages, so in 4 years that is 20 million euros saved solely on wages on one players. Another big earner is Jasper Cillessen and with the fact that he has been quite injury prone and getting injured yet again with Netherlands on a practice match, means that he is likely the other player who is going to be sold this summer.
I believe he is the 2nd or 3rd highest earner in Valencia CF, and while I don't think he can fetch a good price as he is now worth much less than when he was with Barcelona, he could be sold for about 10 million euros, coupled with close to 5 million euros salary, that is about 15 million euros gained, and if Guedes is sold as well, he is likely to fetch 20-25 million euros, plus another 5 million in wages, so Valencia CF is going to be able to balance its books, pay all the outstanding debt for the year and have about 10 million euros to bring in second tier reinforcements. Valencia CF has been linked to few players from the second Spanish division, so the club could bring in few reinforcements from the second division and sign one or two additional players on loan to fill up the ranks.
Another player who is a high earner is Maxi Gomez, and his future also looks in doubt at the club, especially with his poor performances, but his poor performances have also taken a negative effect on his market value, Transfermarkt has his still valued at 25 million euros, but I doubt any club would pay such an amount for him in the current Covid19 situation, especially with two years of poor performance by him. But if a club does come in with a bigger offer, say 20 million euros, Valencia CF is going to sell him.