Every fix-and-flip starts with excitement about the finished product: a gorgeous kitchen, fresh paint, and a happy buyer at closing. But experienced investors know the profit is decided long before the first hammer swings. It is decided by the numbers you run before you make an offer.

This guide explains a popular rule of thumb, how to build a realistic repair budget, and why a contingency line is one of the smartest items you can add.

Start With the After-Repair Value

The after-repair value, usually called ARV, is what the home should sell for once renovations are complete. Every other number is built from it, so accuracy matters. To estimate ARV, look at recently sold homes similar in size, age, condition, and location to your finished product. Focus on true comparable sales, not asking prices, and be honest about differences.

An optimistic ARV is the most common way beginners lose money. If you are unsure, ask an experienced local agent to run comparable sales with you and adjust conservatively.

The 70% Rule Explained

Many flippers use the 70% rule as a quick screen for deals. The formula is simple:

Maximum offer = (ARV × 0.70) − estimated repair costs

Suppose a home is expected to sell for $400,000 after renovation, and repairs are estimated at $50,000. Multiply $400,000 by 0.70 to get $280,000, then subtract $50,000. Your maximum offer would be $230,000.

The remaining 30 percent is meant to cover holding costs, closing costs, agent fees, financing costs, and your profit. It is a guideline, not a law. In a strong market or with cheaper financing, some investors go a bit higher. In a slower market or with expensive financing, they may need to go lower. Use it as a starting point, then build a full spreadsheet.

Build the Full Cost Picture

Beyond purchase and repairs, list every expense you can think of:

• Acquisition costs: title, closing fees, inspections, and any lender charges.
• Holding costs: insurance, property taxes, utilities, lawn care, and loan interest for every month you own the home.
• Selling costs: agent commissions, closing costs, and possible seller concessions.
• Permits and fees: many projects require permits, and unpermitted work can create problems at sale.
• Staging and marketing: photos, staging, and cleaning help the home sell faster and for more.

Time is money. Each extra month of holding costs cuts directly into profit, so build in a realistic timeline and stress test it. Ask what happens to your return if the project takes two months longer or the home sits for thirty days after listing.

Create a Realistic Repair Budget

The biggest budgeting mistakes come from guessing. Follow these steps for better accuracy:

1. Walk the property with a contractor. Ask for a line-item bid, not a single number.
2. Inspect the big four. Roof, plumbing, electrical, and air conditioning can each create major expenses. Have them examined before you commit.
3. Look for hidden problems. Water stains, cracks, mold, termite damage, and old wiring often signal larger issues behind the walls.
4. Price finishes reasonably. Choose materials that match the neighborhood. Over-improving a modest home rarely pays off.
5. Get multiple bids. Compare scope, timeline, warranty, and references, not just price.

Why Contingency Matters

Even the best inspection will not reveal everything. Once walls are open, surprises appear. A common approach is to add a contingency of ten to twenty percent of the renovation budget, depending on the age and condition of the property. The older or rougher the house, the larger the cushion.

Think of contingency as insurance for your profit. If you do not use it, it becomes extra margin. If you do, it keeps a small surprise from turning into a loss.

Watch Your Timeline

Delays are expensive. Common causes include permit wait times, material shortages, contractor scheduling, and change orders. Reduce risk by ordering long lead-time items early, scheduling inspections in advance, and communicating clearly with your team. Set weekly checkpoints and walk the site regularly so you spot problems early.

Know Your Exit Options

A flip is not the only way out. Some investors decide during renovation that a property would be better kept as a rental, and others plan a quick wholesale or partial sale. Having a backup plan protects you if the market shifts. Before you buy, ask what you would do if the home did not sell at your target price within your holding period.

Common Beginner Mistakes

• Trusting ARV numbers without comparing recent sales.
• Underestimating rehab and forgetting contingency.
• Ignoring holding costs and the interest clock.
• Choosing luxury finishes for a starter-home neighborhood.
• Skipping permits to save time or money.
• Falling in love with a house instead of the numbers.

Learn From Each Project

Track every deal in a simple record: estimated versus actual costs, timeline, and final profit. After each flip, review where you were right and where you were off. Over time, your estimates get sharper, and your confidence grows for the right reasons.

Partner With People Who Have Been There

Experience is valuable, especially in a market as varied as South Florida. Working with a team that regularly sources deals, estimates repairs, and manages renovations can reduce the learning curve and help you focus on well-analyzed opportunities. At Happy Investors Florida, we share our own fix-and-flip journeys and work with investors who want to grow wealth through real estate with clear numbers and realistic expectations.

Want to see how real projects are analyzed? Explore our fix-and-flip journey and contact Happy Investors Florida to talk through your next deal.