This is what I would do if I am you, not legal advice or financial advice.
Depends on your numbers. If you were to rent out your primary, how does the cash flow look like? If you are losing money, sell your home (wait till after 12/31 so you can keep the taxes for another year), downsize to rent a place with half of what you are paying in mortgage now, and take the proceeds to invest. If you are having great positive cash flow or are breaking even, refi 80% ARV to a conventional 30, cashout, rent out your primary, and downsize to rent a place with half of what you are paying in mortgage now. Reason being, 1. I would never buy a property that didn't at least break even as a rental. The smaller return has to come with way higher potential for appreciation. So if your property is losing money, that neighborhood is not a rental type of neighborhood, so get out. But the hefty capital gains taxes is tricky so try to delay paying it by selling it after the end of year.
2. If your current primary is a good rental hold on paper, congrats. Now you have a cash generating machine to fund your other purchases. Do a cashout refi or take a 2nd cashout mortgage, and use the equity to buy other properties. Money you get from a refi is tax free until your sell your property so you will be able to use all your equity during the growth phase of your investing. Some principle as a 401k plan, the more you use for seeding in the beginning, the faster your investment will grow.
Yep, the prerequisite is to learn to do your numbers really carefully and really well.