Water is soaking passenger side floorboards. Probably happening for awhile but recently got much worse. I pulled up carpet and felt underneath and found probably close to a gallon of water. Is this a windsheild problem or air conditioner. Water is clear and non oily.

I'd take a look at the factory service manual to see where the drain is.
www.nicoclub.com/fsm

Does the water happen after you've been running AC, or after it rains out?

I searched all service manuals and nothing showed when drain tube exits car or where it runs inside cabin. I'm not sure whether it is after rain or after running ac. I have noticed moldy smell before but this time it seemed to get really bad after a rain so I'm thinking it is a seal under cowl but can't be sure and wanted to clean out drain first. I pulled up carpet and found standing water and everything wet under there up to behind dash but mostly at the bottom of foot wells in front and back passenger side.

On an older car the sunroof drains can get clogged, that may be your issue. Be careful not to use an air hose to blow them out because the drain tubes can come loose. Many dealers, and other places, can clean the drains for around $100 to $125. You might want to go this route if you haven't done it before.

Cleaned sunroof drain tubes and hasn’t happened again but haven’t have heavy rain either

Did you take it to an Infiniti dealer or DIY?

Speaking of expensive.... I have a 2015 Q40. There have been quite a few rain storms in the area. I noticed my passenger side front and back floor boards were flooded. I took it into Infiniti dealership for service yesterday. I was quoted a $2417 estimate to repair sunroof drains. I'm a bit gobsmacked as I have noticed this has been an ongoing issue for many years with Infiniti sedans.
These are the estimated cost of repairs.
As listed:
1. REPLACE LEFT AND RIGHT FRONT DRAIN HOSES AND DRAIN CONNECTORS
2. REMOVE CARPET FROM VEHICLE AND ALLOW TO DRY
Does this seem to be price gouging? If so what should I expect to spend?

That seems excessive. I've used old bike cables (shifter or brake... could also use a throttle cable) to snake down the sunroof drain holes to blow out any crap. Dry the carpet yourself (hit it with a wet/dry vac, park it with the heat on and the windows down, or put a fan on it, etc).