Basics

A D3D For as little cost as possible
Not one based of e waste, for standardization purposes, although these can be made for cheaper
Most likely will have a small print bed, use low melting point materials, and will have to move slowly, but may be useful for small parts, and for building additional machines
As of now this is experimental due to the The "Poor Can Only Afford to Buy A Tool Once" Issue

Industry Standards

A small yet incredibly capable machine
A Review by the Youtube Channel Maker's Muse
A Maker's Muse Affiliate Link to it's Bangood Page ~170 USD as of 5/18/2020
Is a H-Bot Gantry style CoreXY FDM 3D Printer
It uses a Bowden Style Extruder , but otherwise is pretty great
Also has bad (loud, and most likely not the best capability/precision wise) Stepper Drivers , but otherwise has a good board ( need to find what brand/what layout/smd's )
It had a COLOR TOUCHSCREEN (on a sub-200 USD Printer...)
Had micro sd, and usb (or was it serial, double check this
Cooling was not the best, but workable
- Also it can print holder brackets for extra Part Cooling Fans etc
Also has some shipping / assembly issues, but arrives fully assembled
- ie may need some bolt tightening etc

A Design by a Sub-Group/Partner of Digital Blacksmiths uses e-waste
- They also have a cnc machine, may be worth a look
- Also should share the D3D and D3D cheap concept with them

100mm^3 or so bed (need to see axis flex etc, may be able to push that limit a slight bit
Most likely cantilever design, but this can be looked into
RC Servos or some super cheap motor, and perhaps a geardown if needed
make some sort of mini-universal axis system, smaller rods etc?
How cheap can the board be? OCI or somthing ots?
Seems there are SOME cheap hotends, e3d makes This ~30 USD Model
Perhaps use a usb drive for files, as they are more common than sd?