New, Used, or Lease? And WHEN?

As a small business owner it has been nothing short of challenging to build a business from nothing. I came from nothing and have built this thing from the ground up. I didn't have a lot of money.

When I first started I couldn't afford company vehicles. I eventually bought used vehicles in the $20K-$30K range and financed them and that was fine until I unexpectedly slowed down and had to sell off my trucks just to survive.

Once I rebuilt from the slow down I decided to buy used vans around $9K to $10K cash. Right now I have 6 vehicles. One of those vehicles needs major work done. And the others are all 100K miles or more and I feel like they are just ticking time bombs.

I want the reliability of newer, or leased vehicles but the risk intimidates me after my struggles in 2022. Is there a formula for when you should go from paying cash for used, to financing newer/new, and to finally leasing? Is there a revenue metric, a number of vehicles in your fleet, or some other sign that going one route over the other is more advantageous or less risky?

Thanks for taking the time to read this and share feedback!