Quote from @Tim J.:
I would keep the condo, don't pay additional principal. That's a great loan rate. Within a few years it will be cash flowing well AND will have appreciated. There will be frictional costs and non-monetary costs for selling it and then buying something else to replace it.
If you can't afford to throw in a thousand or two or three a year to cover your costs, maintenance, vacancy then sell it. But if you can handle the costs without it putting a burden on you financially then definitely keep it.
I agree here I had a single I was upside down on I had purchased in 2005 during the previous housing sub prime euphoria. The fact it's in DC is huge, team that with the fact you have a low mortgage rate I would try to hold on to this but invest new money in something else.
I got into real estate investing by accident and it's totally a side hobby/gig as everything I do is for passive income as to focus on my regular job. Long story short I was only netting $300 on a single family we had purchased during the peak of the interest only era, now that same house nets me $1600 a month in cash flow after everything, increased in value substantially more, the tenant has been paying my mortgage down for years and my loan is roughly 40% of the value of the property. Real estate is like a fine wine....