Sorry, can’t provide actual contract samples for obvious confidentiality reasons. Mine are customized to my own way of doing things which may not suit your needs. Surely there are CORE resources that can provide you generic forms, as you can also find in many business books devoted to consulting work.
Broadly, I start with a detailed description of the parties involved (may be more than 2), the overall results to achieve, followed by a breakdown into any number of development stages expected along with delivery dates I commit to. Fees, deposits and deliverables for each phase are specd. out. Keep any additional clauses and conditions minimal and simple, people aren’t buying a hotel from you.
You should get paid in full on completion of each phase and NEVER start the next phase without a down-payment. It makes both yourself and your client responsible and usefully anxious. People respect only that which they pay.
Try assembling a small, diverse team instead of being a one-man marching band, your saleability will increase a thousandfold, as will your firm’s capacity to deliver more, better and more varied projects. You’ll also lose the “unfed freelancer” stigma that way.
Again, read up and talk to others already doing it. Core also posts some very good design business stories you can relate to. No matter what, though, it’s uphill all the way, and that’s putting it mildly.
If you’re young, healthy and - ideally - mortgage-free, the excitement is still proportionate to the effort and challenge ahead. Best of luck.