When Sherilyn Faluta bought her first home in July this year, she had no idea that within two months she’d be spending tens of thousands more on repairs.

Even though she had a home inspection before purchasing it, no one discovered the major plumbing issues that led to water damage — and extensive mould — throughout the home’s heating and cooling system. The mould testing and remediation are expensive, and the floors in the kitchen and laundry will also need replacing due to rotten wood.

It will cost close to $30,000 to make the house whole again

Worse, the mould in her new home has made Faluta ill, and she’s had to move out to have repairs done. “It will cost close to $30,000 to make the house whole again,” says Faluta, 40, who lives in North Carolina in the US. She’s already spent nearly $10,000 on repairs, not including what she’s spending on hotels — she estimates about $1,600 per month.

If your newly purchased home has serious issues, resolving them can take over your life. And it might be something completely unexpected. “I moved to my house in 2003, only to find out several years later that I’m on an abandoned coal mine,” says Virginia Nolan, who lives in Michigan in the US. She’s since dealt with cracked walls and foundation and water issues.

Home repair and maintenance costs can add up quickly. In the US, more than half of homeowners experienced an emergency home repair in the past year, according to a survey from home repair plan provider HomeServe USA. In the UK, 5% of consumers’ total housing expenditure goes on maintenance and repair, according to the Office of National Statistics.

Sometimes, hidden problems can create national crises — in New Zealand, shoddy work with timber framing from 1994 to 2004 affected as many as 89,000 homes and cost an estimated $11.3 billion to fix, according to a PricewaterhouseCoopers report. In Canada, tens of thousands of British Columbia condos built with faulty construction continue to need repairs to stop continual leaking.

If you've been sold a lemon, what should you do? Most people in that situation want to hold someone accountable, which may mean suing one or more involved parties. But, before you pull out the big legal guns, here are a few things to consider:

What it’s going to take: You’ll need a strong constitution, because you’ll likely be searching for someone to take responsibility for the problem — your inspector, your homeowners’ insurance, or the previous homeowner, among others. You may have to sue, and you may end up being out of pocket for all expenses anyway, depending on the situation.

You don’t know what you don’t know, and you can’t find what you don’t know to look for

How long to prepare: Before buying property, have it properly inspected by a professional, “whether it’s a certified home inspector, general contractor, or specialist contractor like plumbers or electricians to evaluate particular systems,” says Timothy Frie, a real-estate agent in Florida. “You don’t know what you don’t know, and you can’t find what you don’t know to look for.”

This generally happens a couple of months before closing on the sale of a home, but the earlier you can bring someone into the process, the better. Many home contracts contain an inspection contingency clause allowing the buyer to back out if the inspection turns up major issues.

“Before you sign on the dotted line, ask for proof of when the boiler, central heating, windows, electrics, plumbing and roof were last given TLC and that any building work has been given official approval,” says Hannah Maundrell, editor in chief of UK financial website money.co.uk.

To ensure you aren’t missing anything, consider buying a comprehensive homeowners or building insurance policy that includes protection for legal expenses. “This can help if a defect comes to light after completion, because the buyer might be able to obtain cover for some or all of the legal fees incurred in pursuing the surveyor or solicitor for negligence,” says Lorna Munro, a partner at UK law firm Blake Morgan.

Do it now: Document everything. Take photos of the problems and make an itemised list, with quotes, of repair tasks or renovation projects that will have to be done to correct the issues. That includes a list of construction work, materials needed, equipment and associated labour costs.

Check local law. If you believe that the homeowner or real-estate agent did anything to hide defects from you, you may have a good legal case. In some areas, homeowners are required to disclose all known material facts about a home that could potentially harm its value, Frie says. But the extent of what’s required can vary, so research your local statutes.

Call your estate agent. Your agent is a good place to start, because of their involvement in the purchase of your home. Good agents can work through complex and complicated issues and offer perspective on what is going on” says Michael McGrew, a real-estate agent in Kansas and member of the National Association of Realtors.

Check your inspection. Did the inspector specifically look at whatever it is that is now a problem? If there’s nothing on the inspection that indicated that he or she saw something was wrong, maybe it's a missed issue. If so, the inspector may well have insurance for this kind of problem.

I have been sick for weeks, I have missed work. This has been an extreme financial burden - Sherilyn Faluta

Call your home insurer. Your homeowners’ insurance may cover your particular issue. In Faluta’s case, her home insurer only covered one incident of toilet backup for $2,600, but that’s better than nothing. 

Get moving. “There are strict and varied time limits for claims to be pursued, and the owner will be under a general obligation to mitigate their losses,” says Elliot Elsey, senior associate in the commercial litigation department at Russell-Cooke LLP in the UK. “You should contact a solicitor as soon as possible if you think you have such a claim.”

Do it later: Check your contract. You may have a mediation clause that requires you to pursue mediation before taking anyone to court. Mediation can often be a cheaper way to solve issues, McGrew says.

Do it smarter: Sue as a last resort. If you can’t get what you need after contacting everyone you can think of, it may be time to pursue legal action — but know that you can’t un-sue. “Once you throw that gauntlet down, it’s pretty hard to come to a friendly, mutually beneficial conclusion,” McGrew says.

Faluta has found a lawyer to take on her case, and plans to bring litigation against the inspector and the seller of the house. “I have been sick for weeks, I have missed work,” she says. “This has been an extreme financial burden.”

To comment on this story or anything else you have seen on BBC Capital, please head over to our Facebook page or message us on Twitter.