Do any adults in the house play or plan on learning? If not, for a 5yo child, definitely rent or buy a decent full sized keyboard. You just have no idea if they are going to be playing in a few years. Decide later what to do when you have an idea of how serious they are about it.

I play and bought a used upright about 8-9 years ago after looking for over a year. I got a total steal. Like cars, I’m really not sure why you’d buy a brand new piano. My 3 kids all play now and I don’t plan on ever upgrading to a baby grand/grand. Yes, I can tell the difference and grew up playing on a Baldwin grand (my mom plays as well and is a total piano snob) but there’s just not enough of a difference that I can justify the $ and household space for it unless one of the kiddos got very serious about it (and I don’t see that happening so far).

We have a keyboard as well which let me tell ya, that has the advantage of HEADPHONES my friend! Sometimes after hearing 3 sets of piano practice I send them to their room to go goof off on the keyboard instead for my own sanity.