Great suggestions above.
Much of this depends on the knowledge you have already. Getting educated is important, but you'll reach a point of diminishing returns if you aren't also out there building relationships. There's only so much a passive education (books, podcasts, blogs, etc.) can teach you. When all is said and done, this is a relationship business, and the most valuable education comes from taking action.
Time is your most valuable resource, so task #1 is finding efficiencies in your schedule.
Twelve-hour days are unsustainable for the long term.
You need to make time in your day (30-90 min) for finding and connecting with deal sources - brokers, owners, and influential third-parties. This will accomplish two goals: 1) it will build your pipeline and 2) you will gain exposure to opportunities that cost little to no money.
I don't know what you did to get the credit score you have, but it may be helpful to seek reputable counsel to help get that score up. This may take some time, but it shouldn't stop you from building a network and deal pipeline. You may have to wholesale a few deals to build up a war chest while your credit score improves. Just don't get emotionally married to any deal. Think of it like selling widgets.
Finally, I'm not a huge advocate for scrimping and saving to claw your way out of a financial rut. This contributes to a scarcity/fixed mindset at a time when you NEED an abundance/growth mindset.
Make a plan and consistently seek daily progress toward the objective. Your dream of 50 doors may not be two years away, but you could definitely reach that goal in five with the right approach.