... when we retire in around 15 years.
My fear is if we don't move on this now in 15 to 20 years who knows what prices will be and doubtful we can drop 500 to 600k on a second home. My husband will have a military pension...
I get this question a lot.
First, your spouse is 15 years away from that pension. It's impossible to predict what will happen during those years, and there's a >80% chance that you will decide to leave the service before vesting the pension. It's totally unrealistic (even a fantasy) to expect to stay on active duty for over a decade and a half. If you rewind your life 15 years back from today, would you have believed back then what you're doing now? Yeah.
Take active duty one obligation at a time. If you're not feeling challenged and fulfilled then leave active duty for the Reserves or Guard. Your spouse can still reach 20 good years (for a military pension at age 60) without risking everyone's emotional, psychological, and physical health.
Next, you're right that you can't predict prices 15 years from now. However you can predict that most real estate will appreciate (in the long term) at about the rate of inflation, and that real estate values will oscillate in cycles around that line on the graph, and that some homes will be bargains due to neglect or local factors.
In other words you could invest your down payment fund in equities for the next 15 years. The statistics predict that you'll earn more than the rate of inflation (after taxes). You can cash out anytime during the 10th-15th year to create the down payment fund. (It's the same as building the college fund for a new baby.) When you're ready to start searching for that second home then you can move to the area, rent there for a few months, and learn the details of the neighborhoods while you're searching for bargains.
You don't have to buy today just because all the good homes might be gone by 2030.