what is a low cost camcorder with manual focus capability, external mic jack, and earphone jack?

I think the Canon HF G series meets the technical requirements of having manual focus capability, external mic jack, and earphone jack. I don't know if it meets your budget requirement. Some of the higher-end Sony HDR consumer camcorders will meet the technical requirements, too.

Camcorders can range in price from about $80 to $80,000. The items you list as requirements start appearing in the $1,000 and above range. If you drop the external headphone jack and use the AV-out to monitor audio (so you need only manual focus and mic jack), then you may get to the Canon HF M or above... You cannot control the headphone volume unless you get/make a little amplifier that goes between the headphones and camcorder...

Camcorders with hard drives are practically non-existent. They've all gone to SD cards or internal solid-state memory.