@Mike Nuss, @Amanda Coleman, and @Jay Hinrichs all have great advice. In fact, many people can offer great advice, but ultimately, what matters is the advice that works best for you.
What I wonder, @Account Closed, is what are your long-term and short-term goals? You're on BP, so presumably, you want to invest in RE. If your near-term goal is more financial freedom via passive income, and your expenses are already low, then holding the property for now would seem to make sense. If you want a wad of cash to invest in something else, then I suppose you could sell it. But consider what you would actually have were you to do that--would the amount you have left over in cash allow you to buy a property in the area in which you could both live and cashflow, and if so, could it appreciate and cashflow at the same rate as the property you currently own? Is cash flow even your goal?
I'm a buy and hold gal, so my advice is biased based on that. But I'm also a numbers person, so my advice would be to do what makes sense based on the numbers as it relates to your specific goals. You'll consider things like:
- What part of town do I want to live in, or do I need to live in Portland at all?
- How much cash flow do I want today, or is cash flow important to me right now at all?
- What's my long-term goal, and how would keeping this house get me there? How would selling it get me there?
- If I sell the house, how can I first increase its value to get the highest return possible? Do I think this is the top of the market or do I think there is room for continued [average to good] appreciation?
- If I keep the house, how can I invest in it to get the highest ROI in terms of monthly cash flow?
These are just a few things to consider. I'm a big fan of putting all my options down on a spreadsheet and comparing the numbers, both current and projected. Without having more details about the layout of your house and garage and lot, were I in your shoes, I would see if it's possible to convert the garage to an ADU and what the lowest cost to do that would be. For example, if I can run water/sewer and electricity out there, insulate the walls, add some windows, drywall, finishes, and appliances for $30k-$50k, that's less than any unit you could buy anywhere in Portland. Then I'd live in the converted garage and rent out the small house. (It may make more sense to build new, BUT there are a lot of factors that go into it, like zoning and setbacks and what condition your existing garage is in and is there a loft space etc. For example, if your current garage is in the setback that would now be required by code, it's grandfathered in and you probably wouldn't want to completely demolish it. You might keep that one wall and build a new ADU around it.)
But before renting out the house, I'd see if there was a way to get a third bedroom in there. 1,000sf should be adequate for 3 bedrooms. Could I convert an attic? Is there a basement? (And if there is, that adds a whole new dimension to the story.) Is there a dining room that could be turned into a bedroom without disrupting the functionality of the house? I've noticed that 3 bedrooms rent for about $500-$800/month more than 2 bedrooms in Portland. (That's super general and depends on the area, but the point is, 3 bedroom houses are in demand.)
If I had more specifics about the location and layout of your house, I could give you better numbers. Rentometer.com and craigslist are good places to check rents.
Another option for that site would be to rent yard space to a person with a tiny house. I've heard that people are willing to pay between $400 and $500 just to have a place to park and live in their tiny houses. There are some code issues that you'd want to be aware of (e.g. the neighbors need to be OK with it) but otherwise it's another way to generate cashflow from an existing plot of land. If cashflow is your goal.
Anyway, if you lived in the converted garage, you could still sell your house whenever (as long as 2 of the last 5 years before you sell were owner-occupied) and avoid capital gains tax as Jay described, but you'd also be taking advantage of the appreciation that will most likely occur in that area. If your plan is to sell the house within the next 7-ish years, then keep that in mind when designing your ADU. You'll want something that buyers will think adds value (i.e. the ADU should be nice enough to make people not regret not having a garage, or keep a single car garage, or build new above a garage, etc.)
I have an architecture degree but I don't really trade my time doing drawings for money. That said, I do enjoy giving free design advice and suggestions to nice people who I meet in person. I'm also finishing up real estate school and have been an investor for 4 years in Portland, so I'm happy to provide you my opinions about ways to reach your RE goals and about where I think the value lies within the Portland RE market in general. Feel free to PM and we can chat. :)