But if you’re treating this as a business, aiming to scale up and buy more properties quickly, then the flexibility and liquidity of a 30-year mortgage can outweigh the extra interest.

Most of the lessons you’re anticipating—like managing idle capital or balancing reputation with limited funds—are spot on.For liquidity, I’d look into high-yield business savings or money market accounts with same-day transfer capabilities.

There are still tons of opportunities in the Phoenix market if you're liquid and ready to move.Furnishing it and going mid-term could work, but that adds upfront costs with no guarantee.

Meeting a 20% down payment to avoid PMI seems manageable, although would take a big chunk of my liquid net worth, and I prefer this route over using an FHA loan.

So, I would be taking some money from a SDIRA that I have, not liquidating the entire account either. 

The P&S says:The SELLER shall convey the Premises by a good and sufficient quitclaim deed running to the BUYER or to the BUYER’S nominee, conveying good and clear record and marketable and insurable title to the Premises, free from liens and encumbrances, except: (a) Real estate taxes assessed on the Premises which are not yet due and payable at the time of conveyance; (b) Betterment assessments, if any, which are not a recorded lien on the date of Closing; (c) Federal, state and local laws, ordinance, bylaws, rules and regulations regulating use of land, including building codes, zoning bylaws, health and environmental laws that do not materially interfere with the existing use of the premise as a two family residence; (d) Rights and obligations in party walls; (e) Any easement, restriction, or agreement of record presently in force, which does not prohibit or materially interfere with the use of the Premises as a two family residence.

I tell my clients they should ideally have 25% of the rehab budget in liquidity and at least six months of reserves.

You DONT get into Multi-unit UNTIL you have enough built up in the residential side where you can consolidate the portfolio, liquidate to buy a 200+ multi unit community.

Quote from @Cory E.: Hi James, Feel free to send me a link.

By putting down less upfront, you retain flexibility and liquidity, allowing you to deploy the extra cash into other opportunities, such as a high-yield savings account (HYSA), stocks, or toward a future property.