Tyga -- I Don't Owe Rent ... I'm Buyin' the Damn House!!!

Tyga says the eviction lawsuit his landlord filed against him is bogus, because he's NOT a renter ... he's a homebuyer ... and if he's right it's the most screwed up home purchase ever.

According to Tyga, he plunked $200,000 down on the Calabasas mansion a full year ago and the landlord told him he could move in during escrow, without paying any rent.

If that makes no sense, get this. Tyga says the escrow was supposed to close many months ago, but didn't because the seller didn't provide Tyga's bank with info that would allow the loan to be processed.

The landlord begs to differ, and says Tyga is a squatta.

His lawyer, Lee Hutton, tells TMZ, "We evidently live in a world where a man's word is no longer your bond."

And that reinforces the age-old maxim ... get it in writing.