@Jon3948
I don't know what it is like in your location, but I buy a lot of my linens from TK Maxx/Homesense (TJ Maxi in the US, I think). It's not the cheapest option, but I find quality linens at seriously reduced prices there, including 'hotel style' ones with high thread counts. I would, however, avoid very high thread counts (e.g. 800, 1,000). As soft and lovely as they are, they are not very hard wearing, and you want something that you can not only wash frequently, but treat for stains etc.
One of the best investments I have made for my listings is super thick (10cm/2.5 inch) mattress toppers, but you can get even thicker ones. The ones I have are machine washable, but you do need a fairly large machine. The mattress protectors and sheets go on top of them though so they don't have to be washed between every stay. Since I got these, every single guest - and I do mean literally every single one out of hundreds) - says the bed is super comfortable.
I was lucky enough to find these toppers at a big discount, but even at full price, they are worth it as it's a lot cheaper than buying expensive mattresses, plus they offer additional protection for the mattress. The company I bought them from a company called Groundlevel, but I'm not sure if it exists outside of the UK.
I also provide a variety of pillows in each room, e.g. different types, thicknesses and firmness as people really vary in their preferences for those, and some people are allergic to the feather/down ones (also not great for vegans!).