Direct drive motors are the only ones that won't freewheel (e.g. won't drag when you're not pedaling). Geared hub motors can freewheel because it's inherent in the design, and mid drive motors usually come with a freewheeling adapter. I'm a huge fan of being able to continue riding the bike once the battery is flat, and probably would not build a direct drive bike unless it was for a very specific purpose.
Ebikeling seems to have 26" 500w front wheel geared kits in stock:
ELECTRIC BICYCLE 36V 500W GEARED FRONT 26” KIT (OPT2) | e Bike
Pair that with 2-3 of the $30 eBay 4.4ah 36v battery packs and you're good to go. Might not be a bad idea to get a torque arm, but if it's a steel frame you'll probably be fine.