These are largely the ramblings of a grey-haired ol' man, but several things come to mind. The Snapper RER the OP is discussing is a single blade fixed height mower with an open engine compartment and a seat-forward operating deck to add weight to the front wheels for good traction and turning. I'm not sure what kind of transmission it has: variable speed or hi-low 2-speed. Those mowers were manufactured for homeowners who didn't have the amount of lawn to justify a large lawn tractor. The RER models are excellent performers on smooth ground and small lawns with lots of tight spots and turns. The Snapper is a great little mower with very limited mechanical functions that change or are adjustable. Somewhere on my junk pile of stuff I intend to carry to the metal recycler, I have a 28" Lawn Boy with 5 hp engine. It was one of my favorite mowers of all time for my city house lawn. It was also nearly bulletproof except for the Briggs & Stratton engine that finally failed.
To try and find something similar today is like running a classified ad in the newspaper for $5/hr laborers. 28 years ago, you may have found somebody worthwhile with that ad, but today you won't have any takers. If you do find someone, they'll be worth less than $5 per hour and probably more of a liability than an asset. It's a bit of a stretch, but I see the JD LA-series and D-series mowers about the same as that low wage laborer. If you want anything out of them, you are gonna have to give them unlimited attention and coaching. With the JD low-end mowers, you can get them to perform, but you'll have to limit what you want them to do and you'll have to spend a lot of time on maintenance. I own one of those mowers and my opinions have been posted in this forum before. Having it to do all over again, I would have spent more money. However, if all I have is $1500 to $2000 to spend today, I'd recommend doing a refurb of that great Snapper or looking in the used market for some value at a bargain price. At today's prices and the added features we want in our lawn tractors, you just can't buy 28-year trouble-free operation like you could in the past. It's a different time and the standards have changed.