NEW YORK ( MainStreet) — Call this time the best of time for renters in most big cities and know of course that just a very few years ago it was the worst of times.

It's all about supply and demand and, circa 2010, as the fallout from the housing meltdown scattered debris everywhere, rental units especially at the higher end were in tight supply. People may have lost their homes, but they still wanted to live well and they flocked to rent.

Ditto for others who just began to view home ownership with skeptical eyes. To them, the no-strings-attached flexibility of renting resonated.

Add in the fact that very little new rental inventory was coming into the market and it was a perfect storm that drenched renters, while benefitting landlords who could push rents up.

Flashforward to now and, suddenly, it's becoming a renter's marketplace. Plenty of new rental inventory is flooding the market in most cities. Meantime, enticingly low mortgage interest rates (still near historic lows) coupled with housing prices that may be as much as half off 2007 highs are luring home buyers back into the game.

Which is to say it again is all about supply and demand except now the winners shape up to be savvy renters who know to ask for concessions from landlords, both at lease signing and - most definitely - at lease renewal.

But you may have to ask. Landlords are not necessarily advertising the availability of tasty concessions - but know they can be had in much of the country.

Even in Manhattan, traditionally the tightest rental market in the land where vacancy rates of a single point are common (Citi Habitats recently pegged it at 1.28%). But poke around the Urban Edge NY website, and you will find a lengthy list of Manhattan buildings offering everything from a month's free rent to waiving the monthly amenities fee.

If it's happening in Manhattan, how sweet are the deals where you are?

Concessions vary significantly from market to market. Wherever vacancies are creeping up, expect deals to abound.

In Chicago, for instance, Garrett Jones, who works with the luxe Trio Tower, said that while six months ago, you did not see concessions, now they abound.

He indicated that Trio Tower will routinely throw in one free month on a 15 month lease. Some renters in prime Chicago, he said, are asking for and getting free parking (valued at upwards of $200 per month). Others are asking for and getting for free what in Chicago is called a utility package - heating, air conditioning, Internet access - also valued at upwards of $200 per month.

Jones indicated that right now is a prime time to ask for concessions, precisely because winter is coming and the rental market halts in Chicago once the snows start.