While valves do need to be kept track of, they do not usually need to be checked nearly as often as the book says. My '08 Vino 125 with 24,000 miles has had the valves adjusted once, and then just to get them perfect. They were within spec. And that is an engine half the size of the Helix, and run at WOT 90% of the time. I check the intake every 1000 miles when I change the oil, because it is right under the oil filler cap. I do not use any timing marks, just make sure the valve is completely closed. The Vino has a kickstarter to turn the engine over with.
I would not hesitate to buy a Helix in decent condition at the right price. If I had a choice between a brand new Helix and a brand new Elite 250, it would be a toss up, mostly because I like the looks and maneuverability of small short scooters. But the Helix would definitely be more comfortable on a long ride, which is what I mostly use my scooters for. I am currently setting up my Zuma 125 for long distance non freeway touring.
I won't spend more on a bike than I think it's worth, but if it's a good deal, I don't seem to have a problem buying bikes I don't need.
2002 Vulcan 750, 2013 Royal Enfield B5
2001 XT225, 2009 Genuine Stella
1980 Puch moped