Friend down the road built a pit of sorts. Its on a down slope next to his garage. Three sides of poured concrete and floor, open on the downhill side to walk out of it, with I beams across the walls supporting the ramps. Safe as its not a true pit, open so fumes can escape on the downhill side, and its strong, he has had his small bulldozer on it for an oil change.
He recently added a steel carport shelter over it..
If you have plans to build a real pit, hole in the floor, please, for your own safety and that of others, adhere to the electrical code, and use the proper sealed vapor proof boxes, switches, light fixtures, etc. Also provide it with proper ventilation, again for your own safety. People have died in pits by being overcome by fumes, so rapidly they could not react or get out. The codes exist for a reason, to keep you safe, and alive.
Not saying to not build one, just saying to use the sense to do it safely.
Charles