Hi Timothy. It sounds like you are on the right track and are very close to putting this all together. GCA is a great option. They will do a 50/50 net profit split in most cases. And they will bring money, tons of experience, accounting, project management, etc. They will want a few contractors to bid the job and you'll have the option to take the project if your quote is reasonable compared to others. If not they will hire another contractor and you'll still get your net profit split at the end.
Another option is to spend some time calling 25+ Hard money and private money lenders. Ask the leaders of the local Rei meetups for good private and Hml lender referrals. Use Google and search "Arv hard money lender" plus your town or nearest large city name Also look at the lender search here on BP.
Come up with a 30 second elevator pitch explaining what you are looking for and what you are bringing to the table. Be nice, honest, open, confident, professional, build rapport. The person on the other end of the phone might just make you a millionaire. Ask them their criteria, rates, Arv-based or LTV based (Arv is much less common but probably better for you as you'll need less cash up front), min/max dollar amounts, geography they like to lend in, etc
Most good hmls have a huge network of contractors, investors, appraisers, etc If you develop rapport, and promise to bring them your business they will sometimes open up their network to help you if there is a missing piece of the puzzle.
Spend an hour or two and put together a portfolio of completed projects with before and after photos, basic numbers ( purch price, Const costs, basic scope of work, holding costs, finance costs and sold price, net profit)
Since you have experience in most aspects of the project except finance, the main missing piece will be filled by a good hard money lender. Go find the right match and enjoy the profits.
For the long run, talk to everyone you know about what you do and that you can help people earn 10% plus returns on real estate secured loans. Over time, you'll have access to more money than you can easily place. Most title cos or RE lawyers (whoever does escrows in your state) will handle the paperwork between you and the private money lender.
Third option is to attend the top 2-4 rei meetups in your area and get known as the contractor that will JV with investors. From my experience, the two hardest parts of the flipping business is finding deals with enough meat on the bone and finding reliable , fast, experienced contractors. If you become known as a contractor willing to work at cost for a piece of the back end, you'll be too busy.
Best of luck!