
Another "pick your poison" signature Weakness. Looking at the two elements, the effect and the discard condition, we get:
The effect: Leo loves allies, and he loves using them up. The worst case is if you get caught with a pricey or critical ally out (say Leo De Luca or Agency Backup) out and nothing in your hand, but Leo loves to cart around a lot of allies, so this is less likely for him than other investigators. He ought to have one of his meat shields ready to sacrifice. Charisma and a few lower-cost allies is a buffer. Guard Dog, Hired Muscle, or Treasure Hunter are cheap to play, have useful abilities, and synergize with Mitch Brown should you find him, and a "big money Leo" can easily pay the "drip insurance" cost for the "pay as you go" allies. Probably the saddest thing is that this card won't feed Leo's beloved Decorated Skull.
The discard condition: You draw it and either pay its cost or shuffle it back in. Pretty simple.
All in all, this is a way below average signature weakness, unlikely to cause even a significant tempo hit, much less tank a scenario.