Have you looked into direct drive motors? They are beer silent because the stator slides right on the truck arm (not in the wheel, but just next to it ) this way, the belt/s, gear/s, bracket/s, cover/s, ect… aren’t even needed, only a prong that bolts onto the rotor and slides through the spokes of your abec 11 old school type non-motorized wheels (for a smoother riding experience rather than the hub motor’s harsh metal “rim”). Air tires offer a superiorly smoothest ride on any surface, as the air pressure substitutes all the extra solid mass needed to efficiently support weight. Softer solid type wheels are for a smoother ride, at the cost of more drag. 100% latex tires used in mobility scooters (look grey inside and out for indoor use, they don’t leave black, unsightly skid marks. Last thousands of miles longer than black (normal) tires and are super puncture resistant. Try to use these without tubes, as tubes create about 10% to 15% drag (depending on how thick they are). Good luck on your build.
P.S.: Ask someone to donate parts or money if you don’t mind asking. Just be sure you need it before asking.