Finding a house they LOVE and having an unreasonable seller who just won't accept what the fair market value of their home is. (IE: fixated on a $$ amount and won't take anything less even when other offers were all in the same ballpark). Losing that house then getting so frustrated they stop looking altogether
Sellers who say they got permits for remodeling/additions and promising to supply them, only to find out way into the process they don't have them
Home inspectors who, while doing their job (and playing CYA) scare the bejezus out of a first time buyer talking about: water heaters functioning but "beyond their useful lifespan" ; or the landscaping is too close to the house and the roots can undermine the foundation (true, but in my area there's 1) not one house that's not landscaped with trees close to the house and 2) most of the houses were built in the 1970's and before so if it's still standing....?)
NOT being qualified for the mortgage they think they are. IE: "don't worry my credit is good and I make a good salary, I know what I can afford". Then the pre-approval happens and their credit IS good, and they USE it ...high car payments, credit cards maxed out (tho always paid on time), so their DTI ratio is too low for their "dream house".
Major inspection issues, or even more minor ones that should be addressed, and the sellers won't agree to repair. Also thinking that every minor glitch in the house is something that needs to be addressed by the sellers because of the inspectors comments (buckleing carpet a tripping hazard so replace the carpeting? Come ON !!.
Unrealistic expectations of what they get for their $$ in a specific locality. Wanting a house with new EVERYTHING, but in a price range that may not allow for that. Or wanting the seller to replace things that will make the house better than when the seller lived there (like old HWH, AC, etc)
Mortgage companies that are NOT on the ball and order appraisals or other necessary paperwork (like condo questionnaires) too late in the game to get to underwriting in time to meet the closing date.
Our state has attorney review. Having both attorneys get into an adversarial situation, which doesn't benefit the seller or buyer, but is all about who's gonna win. Ultimately both parties LOSE (usually the sale)
The house not appraising at sales price therefore no mortgage
Any number of unpreventable natural disasters during a storm like trees falling, basements that never flood flooding.
Not understanding the difference between down payments and additional closing costs/ upfront costs (like insurance premiums) and being surprised at the closing.
Sounds like a lot, but thankfully all of these don't happen in the same transaction.