Renovation, to me, is to replace walls and floors and surfaces in the kitchen and bathrooms. The best way to find out the cost is to get some price quotes.
More often than not, you will find that improving, not replacing, what you have is the most cost effective way to upgrade your home. So, rather than replacing floors, if they are wood, have them stripped and refinished. If they are tiled, first get a tile cleaning/polishing professional to let you know if that route is worth it. Otherwise, if you are handy, you can work with sweat equity and do as much as you can yourself or with the help of friends. I laid a tile floor all by myself by watching how-to videos and asking questions at our local tile store. I went by the book and the job came out incredibly well.
Painting walls is the single most least expensive decorating tool with the most impact. But, the devil is in the prep work to get the walls ready to accept paint and have good results.
Sometimes just replacing cabinet hardware, painting a vanity or your kitchen cabinets, swaping out light fixtures and putting down a new area rug will work wonders in a space. A friend of mine had awful sheet vinyl in her laundry room but it was in terrific shape, so she painted it!! Yes, she painted her sheet vinyl floor. Here we are three years later and it still looks great! She got the directions/information on Pinterest.com.
Refreshing a home does not have to cost you tens of thousands of dollars when there are products and ideas to upcycle just about any surface. I was about to sell a house that two of the bathrooms were in great shape, but one vanity was so outdated and the other formica top was stained but in great shape otherwise. I bought rustolium's counter top paint for one vanity top and painted the other oak vanity a great shade of gray and put in updated cabinet hardware. The buyer LOVED it. Two upgrades that cost under $89.
Like another user suggested, clean everything to the bone and then reevaluate what you have to work with. If you have ugly carpet, get rid of it if it cannot be cleaned. Heck, you can, for now, paint the subfloor or stencil it to look like tile. Check out Pinterest.com for so many ideas on how to upgrade just about every surface in your home without spending lots of money.
There is this very odd procedure to finish floors with, get this....paper bags. Yeah, strange. I saw this for myself on a concrete bathroom floor in a basement. It was absolutely beautiful. Also, on Pinterest.com.