If you would like your husband to have a larger office, then get a job now. That's your safety net, even if you have to make egg rolls at the Happy Palace on Garrett Road or fix faucets for Devlin's Plumbing on North Durham Avenue. Use those earnings to pay for the new office, but keep that $21,000 in an interest-bearing account for “just-in-case” money.
If you do build a home office, be mindful that you're unlikely to recover the cost on a resale (homes are no longer good investments) and that renting the space at some future date would be more trouble than you can imagine. Finally, unless your husband discovers a Golconda or unless you find a job, your husband — like many other 57-year-olds today — may have to work till he's 75. Accept the fact that your husband may have to work another 20 years. It's taken six years for your retirement plan to come back to even, and the future years are likely to be as unproductive.
Please address your financial questions to Malcolm Berko, P.O. Box 8303, Largo, FL 33775, or email him at firstname.lastname@example.org.