If I have a unit with 1 might, playing with Rengar legend and play Kinkou Initiate, can I use the Rengar legend ability to add 1 might to a unit on play before the Kinkou Initiate ability goes that says on play if you have units totaling 5 might draw a card?

Yes, you can sequence these effects so that your unit's Might increases before checking the condition for Kinkou Initiate.

The Ruling

When you play Kinkou Initiate, both its "When you play me" triggered ability and your Pridestalker (Rengar Legend) triggered ability trigger simultaneously because they share the same trigger condition ("When you play a unit").

As the controller of both abilities, you choose the order in which they are placed onto the chain (Rule 333.1). To achieve your goal:

1. Play Kinkou Initiate: It enters the battlefield.
2. Place Triggers on the Chain: You choose the order. You should place the Kinkou Initiate ability on the chain first, then place the Pridestalker ability on top of it.
3. Resolution (LIFO):
   • The Pridestalker ability resolves first: You target a unit (including the Kinkou Initiate you just played, per RiftJudge FAQ #9769) and give it +1 Might.
   • The Kinkou Initiate ability resolves second: It checks the total Might of your other units (at this moment, your total Might is higher due to the Pridestalker buff) and determines if you draw a card.

Important Notes

• Triggering Condition: Kinkou Initiate's ability states "draw 1 if your other units have total Might 5 or more." This check happens on resolution (when the ability is processed from the chain), not when the unit is played.
• No Official FAQ: This specific interaction between a Legend trigger and a "on-play" unit ability is not covered by an official FAQ, but this is the standard interpretation based on the LIFO (Last-In, First-Out) resolution of the chain and the rules regarding simultaneous triggers.