If you are looking at cheap.... I have noticed P90s nowadays are dirt cheap, and super easy to work on....
Plastic bodies with metal uppers usually... Since you are like hugging it, and with them being so small, not much to worry about breaking.
Don't forget they have supposedly one of the strongest mechboxes too
Echo1/KS P90s are dirt cheap, CA P90s are pretty cheap nowadays too... Although CA gears are hit or miss in regards to quality control? (My CA P90 gears have different widths on each end and yeah, had to replace them...)
On the other hand, Full KS P90 drop in gearbox kits are under $40 if you want to save money.
Wouldn't hurt to get a Thompson since they are cheap, and use the same gearbox too... Let's you have the option of doing a WW2 loadout when you're bored too :P