If you can’t afford a professional and you’re set on a DIY solution to fixing wood floors that aren’t in terrible shape, but could use a lift, here’s a link to a tutorial from This Old House on How to Refinish Wood Floors. By “refinish” they’re not referring to a full sanding, but to a buff and coat or what he calls “scuff-sand” and a coat.
The main risks to attempting this are swirl marks that are much more visible than a pro would have, and problems with finish adhesion and so forth (issues could arise from simply not following directions/missing a step, or contaminants, or stop and start marks, etc.) There’s certainly risk (See Please hire a reputed professional! article), but This Old House magazine’s article at least has steps to DIY refinish hardwood floors w/ pictures. There are probably video tutorials on YouTube as well. You may want to browse around our Problems With Finish category and others to gain some foresight as a preventive measure.