Most of the cheap bikes you'll run into small issues , but usually nothing that an offset intake won't fix. Alot of folks do their first builds on huffy Cranbrooks. Both the Cranbrooks and their higher rent brothers the Nel lusso build pretty well. For a bit more money (like 350)I did a yd100 on a firm strong urbanman like a year ago and it was a super easy build.wide open. And of course at the higher end are your micargi's and stretch cruisers which are nice and open but will require additional mounts or custom fabrication and long ass chains!
Easy first build = Cranbrook(like 100 bucks from Walmart)
Nel lusso(199 @walmart and comes with a welded on rear rack and a basket)
Another good option is the cdhpower gasframe I have a 3.4 liter and it's a pretty easy build but I paid 325 and got the frame ,fork, headset, petcock and am engine mount. No wheels or pedals you gotta get all that yourself but overall very satisfying