Every experienced mobile home park investor has a version of this story.

You close on a 60-lot park in the Southeast. The rent roll looks solid. Cap rate is a clean 7.5%. You’ve done your walk-through, reviewed the leases, run your numbers three times. You’re confident.

Then, six months in, you get a call. Sewer line collapse. Then another. Then the water pressure starts dropping across the park. The contractor pulls up a section of pipe and holds it up for you to see: Orangeburg. The stuff they stopped making in the 1970s because it disintegrates. Your park has been running on it since 1968.

Three months and $340,000 later, you’ve learned the most expensive lesson in manufactured housing investing.

This isn’t bad luck. It’s a due diligence failure — and it’s preventable.

Why Infrastructure Is the Hidden Landmine in Mobile Home Park Investing

Mobile home parks are different from every other commercial real estate asset class in one specific way: the infrastructure is buried, old, and almost never properly documented.

Most parks were built between 1950 and 1985. That means the water mains, sewer trunk lines, and underground electrical conduits are anywhere from 40 to 70 years old. These systems were installed to building codes that bear no resemblance to today’s standards. And in the vast majority of parks, there are no as-built drawings, no maintenance logs, no pipe material records. The seller often has no idea what’s down there.

The typical buyer walks the property, checks for obvious issues, and moves on. They’re looking at occupancy rates and lot rents. They’re running pro formas. They’re not thinking about what’s six feet underground.

Until it fails.

The Three Infrastructure Killers to Know Before You Close

1. Orangeburg Sewer Pipe

Made from compressed wood pulp and pitch, Orangeburg was widely used through the 1970s. It has a rated lifespan of 50 years — meaning most of it is already past its expiration date. It deforms under pressure, collapses, and causes chronic backups. Replacing a main trunk line in a 60-lot park can run $80,000–$200,000 depending on depth and soil conditions.

2. Galvanized Steel Water Lines

Galvanized pipes corrode from the inside out. By year 40–50, they’re significantly restricted and prone to pinhole leaks throughout the system. In a master-metered park (where you pay one utility bill for the whole property), every galvanized pipe leak is your operating expense. A full re-pipe on a mid-size park typically runs $150,000–$300,000.

3. Polybutylene (PB) Pipe

Popular in the 1970s–1990s, PB pipe reacts with oxidants in public water supplies and becomes brittle over time. There were class-action settlements over it. If you find it in a park, budget for replacement.

The Due Diligence Protocol That Protects You

At Keel Team, we’ve developed a non-negotiable infrastructure inspection protocol for every acquisition. Here’s what it looks like:

Step 1: Pull the history. Before you set foot on the property, request permit records from the county and the original plat and utility maps. If the seller can’t provide utility maps, that’s a yellow flag. If the county has no records, that’s a red flag.

Step 2: Sewer camera inspection — all main lines. Not a spot check. Every trunk line. This costs $800–$2,500 and is the single highest-ROI action in your due diligence process. The camera footage tells you exactly what material you have, where the problem areas are, and whether you’re looking at a $10,000 repair or a $300,000 rebuild.

Step 3: Hydrostatic pressure test on the water system. This pressurizes the distribution system and identifies leaks before you close. If a park is losing 20% of its water to underground leaks, you’ll find out now instead of 60 days post-close.

Step 4: Talk to the longest-tenured residents. They’ve lived there for 20 years. They know which lots flood, which section lost water pressure last winter, and whether the sewer backs up every spring. This information is free and invaluable.

Step 5: Price it into your offer. Even after a clean inspection, any park older than 30 years should have a capital reserves line item for infrastructure. We typically budget $500–$1,500 per lot depending on park age and pipe material findings.

Want a complete framework for evaluating any mobile home park before you make an offer? Our Mobile Home Park Due Diligence Playbook covers infrastructure inspection, financial underwriting, and everything else you need to evaluate before closing.

What to Do If You Find Problems

Finding infrastructure issues during due diligence isn’t necessarily a deal-killer. It’s a negotiating lever. You have three options:

1. Price it in. Get contractor bids, reduce your offer price by the remediation cost, and close knowing exactly what you’re walking into.
2. Negotiate an escrow holdback. Seller funds a repair escrow at closing, released to you once remediation is complete. More sellers are accepting this as mobile home park buyers become more sophisticated.
3. Walk away. If the infrastructure is catastrophic and the seller won’t move on price, walk. There are other parks. There aren’t other $400,000 surprises you need.

The Bottom Line

Infrastructure due diligence isn’t glamorous. It’s not the part of mobile home park investing covered in most podcasts or courses. But in a 40-year-old park with no maintenance records, what’s buried underground can make or break your investment thesis entirely.

The investors who thrive long-term in this asset class are the ones who get rigorous about what they can’t see. They budget for it, inspect for it, and price for it.

The ones who skip this step are the ones posting in forums about their $300,000 surprise.

Don’t be that person.

Keel Team is an experienced mobile home park investment firm operating manufactured housing communities across the Southeast and Midwest. Learn more at keelteam.com.