PCBgogo

Hello!
I'm ready to bring my project to market and am trying to navigate the certification process. I am aware of the standard approach to certification - I just don't have money and time.
My product is essentially just a low voltage power controller running custom software (raspberry pi controlling mosfets to 12V solenoids), and has already been tested on-site by my business partner / pseudo-first-customer. The only custom electronics I built were the power controller boards, using I2C GPIO expanders and mosfets, and a sensor board with more GPIO expanders and some pull-down resistors to measure simple open-close switch sensors.
In order to avoid having to certify this product I thought I could just swap out my custom boards for some off-the-shelf boards from a reputable source, but in looking around I noticed that those boards don't seem to have any certifications either...
So now I'm wondering whether it is at all possible to avoid borrowing a few grand and getting the paperwork, and also how other kit builders are allowed to sell, perhaps because their products are 'educational'?
If anyone has any thoughts or has been in a similar situation before, any advice or ideas would be much appreciated!
Also wondering if I can at least delay the process by selling 'engineering samples' or 'prototypes' while I get the certifications, then have my customers switch out the hardware once I have the paperwork in order...I'm selling to a pretty niche market so the volume should be pretty small at first - though, of course, this is not ideal for a lot of reasons including safety and hassle...
Maybe I can make the hardware open source and sell 'the assembled kit' until I have the money to certify...?