First, even before starting your business plan, check the area, and see if there is a need for your services, too often the desire to go in business , closes the mind, to the critical needs, of a new business, part time, or full time, you will need to get your business plan ready, this is your road map to making a go of it, it is not necessary to have a formal plan, a sheet of paper with your plans on how you intend to operate, and finance the business, what your expected earnings will be, and the markets you will be servicing, the plan is not in stone, it will change with your needs, and business conditions.
You said probably be LLC., do you have an attorney to advise you?
Do you have an accountant to help, before you start off in the wrong direction?
Does your state have lic, requirements?
What insurances will you need, and will they be the proper coverages?
Equipment, and trucks needed?
From my experience, part time did not work well, i had all the expenses, and not eniough hours to recoupe the expenses, it was like a tred mill.