How to Track Renovation Costs by Unit (Without Losing Your Mind)

The Multi-Unit Headache

You just bought a triplex. The rehab budget is $250K. Simple enough, right?

Then reality hits: the new roof covers all three units. The plumbing stack serves Unit 1 and 2. The kitchen in Unit 3 needs a total gut. And your contractor just submitted one invoice that covers work in all three units.

Welcome to the wonderful world of multi-unit cost tracking, where every expense needs to go somewhere specific and nothing is ever straightforward.

The Three Types of Costs

Every expense in a multi-unit renovation falls into one of three buckets:

1. Unit-Specific Costs

These are easy. New kitchen cabinets in Unit 2? That's a Unit 2 cost. Bathroom tile in Unit 1? Unit 1. No ambiguity.

2. Shared Costs

These benefit the entire property. Think:

• •Roof replacement
• •Exterior painting
• •Landscaping
• •Common area hallways
• •Main electrical panel upgrade

The question is: how do you allocate them? Most developers split evenly across units. Some allocate by square footage. Either works — just be consistent.

3. Partial-Shared Costs

This is where it gets spicy. The second-floor HVAC serves Unit 2 and 3 but not Unit 1. The shared bathroom wall between Unit 1 and 2 needed new plumbing. These costs benefit some units but not all.

You need a system that lets you assign costs to specific combinations of units. If you're doing this in a spreadsheet... condolences.

A Practical Framework

Here's how to set this up properly:

Step 1: Create your unit structure

List every unit in your property. For a triplex: Unit 1 (first floor), Unit 2 (second floor), Unit 3 (third floor), plus "Shared/Common."

Step 2: Set up budget categories per scope

Your categories (electrical, plumbing, kitchen, etc.) should exist at each level. So you'd have:

• •Electrical — Shared (main panel, exterior)
• •Electrical — Unit 1 (outlets, fixtures)
• •Electrical — Unit 2 (outlets, fixtures)
• •Electrical — Unit 3 (outlets, fixtures)

Step 3: Assign every cost at entry

When a receipt or invoice comes in, immediately assign it to the right scope. Don't batch it for later. "Later" turns into "never" which turns into "I have no idea where $40K went."

Step 4: Review weekly

Look at your per-unit spending vs. budget. Are you on track for Unit 1 but bleeding money on Unit 3? Catch it now, not at the end of the project.

Why This Matters for Your Bottom Line

Let's say your triplex has an ARV of $800K. Your all-in target is $450K (purchase + rehab). If you overspend on the rehab by $30K because you couldn't track where money was going, that's $30K straight off your profit.

Worse: if you're using hard money, every extra week of construction is another interest payment. (We wrote an entire article on how holding costs silently kill your profit — it's worth reading.) Knowing exactly where each unit stands means you can prioritize, reallocate, and finish faster.

The Tech Solution

Look, you can build an elaborate spreadsheet system with pivot tables and cross-sheet references. Some developers do. They also age faster than the rest of us.

Or you can use a tool that's built for this. Builos lets you:

• •Set up units and scopes in minutes
• •Assign every cost to specific units or mark as shared
• •See per-unit budgets, spending, and health scores at a glance
• •Split shared costs automatically

No formulas. No pivot tables. No 3 AM debugging sessions.

Track your next renovation the right way. Start your free trial.