The result of scale economies should be operating leverage, whereby profits are able to grow faster than sales.
The combination of operating leverage and low ongoing capital requirements suggest that the firms should have plenty of free cash to throw around.
Tell tale signs of good cash generation are dividends, share buybacks, and an accumulation of cash on the balance sheet.
Another characteristic to look for when evaluating investments is predictable sales and profits. That makes financial results more stable and predictable.
Should there be high barriers to entry into this business, the firms in this business tend to have wide, defensible moats.
When they are trading at cheap prices, they are usually worth a good look.