If you live in San Francisco, be on the lookout for some mysterious white envelopes -- they may contain $100 bills.

An anonymous person is dropping off sums of money around the city and then tweeting hints about the locations in a project called "Hidden Cash."

Could you and 25 of your friends use a @Sightglass Coffee? Look in the abandoned phonebox next door. pic.twitter.com/tzh9Ffk6dt — Hidden Cash (@HiddenCash) May 23, 2014

Why not use this to tip your @YogaToThePeople teacher this morning? 🙏 (Find it under the key box) pic.twitter.com/0ERUndkajF — Hidden Cash (@HiddenCash) May 23, 2014

The person behind Hidden Cash told The Huffington Post that the project will soon expand to other cities.

"I am OK with giving out at least $1000 a day for the foreseeable future. It will not affect my finances significantly," he or she wrote in an email. "We are planning to add more cities, starting with LA next weekend, and NYC shortly afterwards."

The donor said they "want to start a nationwide movement" around this anonymous charitable giving.

According to the Bold Italic, which also interviewed to the man or woman behind the project, the Hidden Cash benefactor is a real estate magnate who wants to give back to the community.

“I’ve made millions of dollars the last few years, more than I ever imagined, and yet many friends of mine, and people who work for me, cannot afford to buy a modest home in the Bay Area,” the person told the Bold Italic. “This has caused me quite a bit of reflection. I am determined to give away some of the money I make, and in addition to charity, to do it in fun, creative ways like this.”

After each money drop, a tweet goes out from @HiddenCash with hints about the location of the envelope. @HiddenCash also requests that the lucky recipients tweet photos of their discovery.

The person behind the campaign told HuffPost that she or he is maintaining anonymity for fear of "business associates who may take me less seriously."

He or she also told the Bold Italic that part of the inspiration for the project was staggering wealth inequality in San Francisco. (The city has the largest wealth gap of any city in the country.)

It will probably take more than a few cash-stuffed envelopes to address the broader causes of the wealth gap that the person behind @HiddenCash is concerned about. Nevertheless, it's a clever, generous idea and is definitely brightening the days of some lucky San Francisco residents.

New Drop: Giving Oakland some ❤️. Lake Merritt BART (storage container, bikerack, tree). SF drop in 15 min pic.twitter.com/CJxCVVLkzo — Hidden Cash (@HiddenCash) May 23, 2014

First name of a composer who lived to be over 100 (last name is a European capital) + square root of 49 pic.twitter.com/YcrriWi6jz — Hidden Cash (@HiddenCash) May 25, 2014

Thanks @HiddenCash and congrats for making bank last year ! Congrats sfsu graduates of 2014! pic.twitter.com/Ywfed1PeaW — Brendon Escalona (@iamuser1353) May 25, 2014