curious about Lawn mower maintenance

[Marthe48]

I've had a mower in the basement which hasn't been turned on or used since 2015. My daughter said she'd take it, but hasn't taken it. I'm wondering what will go wrong on it just sitting? Like washers or other fittings? I don't know what brand it is. You can tell me the parts. I might know what they are, but wouldn't know where they are on the mower.

My husband's cousin gave it to him in 2014, because something had gone wrong with it. It was almost new at that time. My husband figured out the problem and fixed it, but didn't use it much as he had other mowers he was using. If my daughter doesn't take it this year, I might try to sell it, but would like to have it up-to-date if I do, or let buyers know what to expect.

Thanks for any advice.