A few more thoughts,
The framer has sold Mary a gazebo that is probably implied to be suitable to pass code and for some service. She might have recourse if it is not. Our local BO was not impressed with one outfit that made those prebuilt sheds. He got them when they provided delivery and set-up services, they then became unlicensed contractors. In his view you can sell anything, it is up to the buyer to seek redress in that case, but, as soon as you build or set it up you are on his turf.
I state what the homeowner will provide, what I will do and what I will not do. They will provide;
Power,all foundation work (oh you meant the porch footings too!), little house on the prarie, all permits, and be responsible for all taxes and fees and any material handling equipment I need.(Some states do require you to be their tax collector, yes I've had to pay the taxes for the entire built value)
I exclude responsibility for bought goods that should carry a manufacturers warranty, or any responsibility for weather related delays. My state also requires a completion date on a contract, I've never included that as it strikes me as a willful lie but they want it in there. I also write out any areas that I know I'm not doing to remove the assumption that I am going to shingle or frame out the basement... yes I've done both for the fun of it by not excluding them.
We then detail the scope of work, I've had a lawyer call this a handshake but at least it gives us the basic talking points.
Payments are detailed at progress milestones. Change orders are to be written up and signed by both parties and are payable immediately. I typically actually bill for them in the end and use judgement in those bills. Sometimes I have felt I didn't explain well and we had an honest misunderstanding that I shouldn't bill them for. Some folk, well, I wish I could charge a "hassle tax" on top of the change

I explain everything as we read through it with the exception of my judgement on change orders, I push them to get it all right in the first place. Promise short, deliver long, you'll be a hero.
I do that in triplicate, we all sign, I get one and only one signature, that is my boss. This keeps me out of the middle if there are marital disagreements. I keep one copy and give them two, one for their files and one for the lender.
A contract is really something that exists in the minds of the parties, it is an offer and acceptance of that offer. The paper is the basis for the discussion but it must be based on the good faith of both parties. It will never cover everything that goes on or goes wrong. If you suspect the good faith of the other party no amount of paper will protect you and no amount of money will make the job worthwhile, talk it out then or politely exit. That suspicion or feeling is not necessarily them, it is likely you, but you must respect it. Life is short, take on the jobs and clients you can do your best with.