I got my 1.5KW spindle and VFD for about 300USD. I needed to get some other items to complete the setup including good quality VFD cable, waterpump, radiator, reservoir, and tubing (approx 500USD for spindle and all accessories). Depending on the lengths of your running time and ambient temperature and size of reservoir you could ditch the radiator all together. I got a 240mm x 120mm PC watercooling radiator and a decent Eheim aquarium pump.
You will still hear all the cutting noises which can be some what loud but not terrible. Dust extraction is still the real killer in terms of noise.
An enclosure is a good option but for me limits visibility and hinders troubleshooting, wasteboard replacements etc. I would always run some dust extraction in an enclosure or not as I would not want the dust/chips getting into the spindle system or the linear rail systems.
A watercooled spindle, a modest but specific designed woodworking dust extractor should suffice and be at a respectable noise level.
If you are doing 2.5D cuts and you get good at selecting the right endmills, tooling paths and feeds/speeds you would be surprised at how fast your projects will take form. Its the 3D carves and intricate engraving that can take considerable time.
Short bursts of modest noise about the same loudness of a household vacuum cleaner shouldn’t disrupt the peace too much