It will be near impossible to make the numbers work on a BRRR deal.I'm treading very lightly right now, but looking for houses to flip from highly motivated sellers in A++ locations.

I'm fairly certain it would be nigh impossible to finish the build in that time, given contractor schedules in my area but I know that I could definitely spend $125k as the total build cost will likely be more like $225-250k (plus the $75k purchase price).

However $400k is merely a drop in the bucket in NYC, and is near impossible to get into multifamily at that budget in this market. 

Of course, it can be almost impossible to validate any rents the seller claims they collected in cash.

Finding deals in this crazy market almost impossible, I know they're out there I just need to pick up the pace!!! 

If you buy without rehab, it will be practically impossible to get a quick cash-out refinance because there will not be a justification suitable for a lender for the jump in value

These style deals were impossible 6 months ago but we're seeing them more now.Last- if your goal is specifically to generate the highest level of cashflow possible you'll have to look at more esoteric management options (rent by room, STR, Travel Nurses) or in markets with more favorable rent:price ratios. 

I know it’s near impossible to time the market so I don’t need to hear that just want opinions on what I should do.

Ideally I’d like have rent cover a good part of the mortgage but seems nearly impossible in the current market situations i my area with high property cost and high interest rates?

Not impossible but really difficult - you're paying someone for that "value add".