In January 2013, “Mr. and Mrs. 1500” – the pseudonym of soon-to-be early retirees Carl and Mindy – had about $586,000 in investments and cash.

They decided to get serious about their savings goals and committed to building a portfolio of at least $1 million by February 2017, 1,500 days later, in order to retire at age 43.

The couple exceeded their goal: They have grown their net worth from $568,000 to roughly $1.47 million. You can see their initial financial standing and current net worth on their blog.

They credit most of their success to cutting expenses and smart, simple investing strategies. Here’s a roundup of some of their favorite resources that helped them cut back and also grow their money.

” The Simple Path to Wealth is all you need,” says Carl.

JL Collins’ book grew out of a series of letters he had written to his teenage daughter about money and investing.

He offers the same simple approach to mastering your money that he offered her, and explores topics including how to think about money and why that’s the key to building wealth ; where traditional investing advice goes wrong and what actually works; and the importance of ” ‘F you’ money .”

The early retirees use the free app Personal Capital.

“We have numerous accounts like 401(k)s and IRAs in addition to several checking accounts in different banks, investment accounts, etc.,” Carl writes. “Personal Capital allows you to link them all on one site, which helps you keep track of all your money more easily than logging into and out of numerous sites.”

An added bonus: Personal Capital offers adviser tools, including a 401(k) fee analyzer, which Carl says saved him “more than $100,000 by warning me of nasty, high-fee mutual funds that I mindlessly invested in.”

Mr. and Mrs. 1500 use Republic Wireless, which uses your wireless connection for calls and texts to reduce costs. “If you like Android, RW is for you,” Carl says. “Our RW phone on the unlimited 3G plan runs about $30 a month.”

Not bad considering the average bill for Verizon, ATT, Sprint and T-Mobile users can be more than $120 a month.

If you’re loyal to the iPhone, consider Ting.com, suggests Carl: “Ting works over the Sprint nationwide network, but does the billing themselves.” The rates depend on how you use your phone – how many texts you send, how much data you use – but the average Ting customer pays $23 a month.

Booking a car online is one of the rare times you have to enter your credit card information. ” Autoslash takes advantage of this to save you money,” Carl explains.

After you book your rental car through Autoslash, the site checks rates and will automatically rebook you when it finds something cheaper. “I booked a car once and by the time I picked up my car, Autoslash had rebooked me four times at a rate that was half the original,” he writes.

Head to the retail giant Costco, which sells pretty much everything.

“We do a lot of comparison shopping and even Amazon usually doesn’t beat their prices,” Carl says. “If you drive a lot, Costco may be worth it for the cheap gas and great tire services alone.”

The wholesale club has a membership fee, “but we think it’s worth it,” says Carl, who shares the executive membership ($110 a year) and the Costco American Express credit card with his wife.

Skip Microsoft Office, which can cost $80 a year, and use Google Docs.

“I see folks spend hundreds of dollars on Microsoft Word when Google Docs would serve them just fine,” Carl writes.

“It doesn’t have all of the bells and whistles of some of the Office Suite, but most people don’t need all of that stuff. … Perhaps best of all, your work is saved to the cloud so all work isn’t lost when your hard drive goes belly up.”

Carl planned on retiring in his 60s until 2010, when he first encountered the Get Rich Slowly blog.

“The author, J.D. Roth, discussed how he attained early retirement by abandoning the ridiculous, debt intensive, consumerist lifestyle that most people seem to embrace,” Carl explains. “My journey had begun.”

He didn’t stop with Roth’s blog: “I started reading about other people with similar early retirement ideas. Mr. Money Mustache, The Simple Dollar, Brave New Life and Early Retirement Extreme all started to open my eyes to another way. A better way.

“The common thread was that financial independence early in life isn’t a silly dream, but an easily attainable goal if you play your cards just a little differently.”