I don’t know a dam thing about this stuff but I wanted to say good luck with your business.
Talk to your agent and specifically ensure your trailer is covered when disconnected from your truck and know all the exclusions to the letter.
Your agent can answer your insurance questions; your State’s DOT can answer the rest.
Really not questions to be asking here...just sayin’.
Good luck.
You don’t need a DOT number unless you haul for others.
Check also to see if you need a CDL to drive it. If so, then expect to have regular medical exams where new federal policies, not doctors determine what is important to know about you and your health.
Make sure for your safety ...both health wise and financial that you are not carrying any materials contaminated with lead (old paint) or asbestos (old plastic tiles and insulation).
For commercial license and HAZMAT info contact your nearest DMV...they have all the pamphlets.
and good luck with your venture.