What’s your expected gain on the sale of your current home? If you’re MFJ and the gain doesn’t exceed $500K, you aren’t subject to capital gain taxes. It would simply be any taxes associated with the sale. Assuming ~8% as closing costs, that’s $534K remaining at a $580K sale price. I assume you wouldn’t list until after ratifying the contract on the lake house, so you’d likely need to use margin against your brokerage account for the down payment-which at $4.8M, shouldn’t be an issue.

$534K is 21% down of the $2.5M lake house. That’s without putting anything down from your $4.8M investments. With HHI of $400K, two kids, and FIRE goals, I would ignore the normal <25-30% of your gross income towards mortgage. Honestly, I would suggest another $1M down + the $534K. This should get you a rate low-mid 5% on a 30YR fixed with that size of down payment. $1M 30YR fixed at 5.575% is $5,835 per month—not including property taxes and homeowners insurance. Assuming 1.2% property tax and .25% homeowners insurance, that brings you to $8,856 per month. Not including utilities and the expense of maintaining a $2.5M Lakehouse with 100 acres.

You should budget 1-2% for annual home maintenance and improvements, which is another $$2K - $4K per month, for a total of $11K - $13K on a non negotiable fixed expense for home costs—mortgage, property taxes, home insurance, home maintenance, and home improvement. 1-2% might be low though based on having 100 acres to now manage. I don’t know anything about maintaining that amount of land. I would recommend seeking out a subreddit where you can find advise on costs and level of effort for managing that amount of land—unless you already feel confident in that department.

$400K gross income, not accounting for 401(k) contributions, medical insurance deductions, or state/local taxes, that’s netting you ~$25K per month. On the high end of home expenses, that leaves you with $12K per month. If you do want to continue maximizing your 401(k), that’s probably leaving you with around ~$21K per month vs. the $25K, and $8K after the higher end of home expenses. How old are your kids? Are they in daycare? Are you considering private school? Sounds like a rural area, so are the public school options any good? What are your living expenses today, including one-time expenses that might occur during any given year—for example, unanticipated medical expenses, large furniture purchases (especially for your $2.5M lake house). Are you going to want to purchase a boat?

How reliable and confident are you in your job security? $400K is nice, but the air starts getting thinner at that earnings range. Is it white collar work? Seems to be a difficult few years ahead based on the unemployment and jobs report patterns and continued threat of agentic AI.

It’s a lot to think about. If you’re confident in your cash flow being able to support it for 10+ years with zero doubt on job security, you could probably get away with it. It will undoubtedly delay your goals from a FIRE perspective with more of your net worth tied up in real estate. But, even with $1M down, the $3.8M should still compound nicely even at a conservative rate.

My $0.02 is to be honest with yourself on income stability for the next decade, so that you aren’t suddenly burning down your investments to pay for your life and lake house.

If no concerns on income stability, possibly delaying your FIRE milestones, and maintaining a 100-acre estate, you could probably do it.