Refinancing requires you to re-qualify for the mortgage all over again. If home values are going up, you maintain your credit rating, your employment is steady, and your income & debt levels don't get worse then it is usually relatively easy to refinance. However what a lot of us loan officers are seeing today is that home values aren't as high as when the homeowner purchased their home, giving them less equity (especially if they haven't paid down the principal balance by the amount their value has decreased) and then that may create a requirement to bring in funds at closing in order to complete the refinance - something that the majority of homeowners aren't too hot on doing.
For example if someone purchased their home for $300k with a 20% down payment (avoiding mortgage insurance) and then their home value fell to $280k when they attempted to refinance, then to continue avoiding mortgage insurance the new loan's principal balance couldn't be any higher than $224k. If the mortgage balance is still close to $260k (what it'd be on a $300k sales price after 20% down), then that would require ~$36k to be brought in at closing (in addition to the new loan's closing costs, unless the lender is offering a special deal where they'd pay closing costs). If that person was fine accepting mortgage insurance, then they could potentially refinance at 95% of their home's $260k value (or 97% with FHA financing), which would be a loan amount of $247k ($252,200 with FHA), and less funds would need to be brought in at closing.
So if you will be able to bring in funds at closing, then you likely could be OK refinancing later if home values decline (barring any other changes to underwriting criteria between when you purchase & would eventually refinance).
Shane Milne | Lending in all 50 states | NMLS #81195