Nothing is a guarantee, but you reduce the risk astronomically when you hire a professional that knows the market, knows how to screen, has solid policies, decades of experience, etc.I manage nearly 400 rentals.

The market went crazy for almost a decade. 

I did this personally for about a decade and my business partner who I did it with has done it all his life 3rd generation logger.there is huge money to be made in Timber if you know what your doing.  

(I lived there for 4 decades before moving to a more affordable state)Your after-tax take home is less than $6,000 a month by my calculations https://www.talent.com/tax-cal... and that does not leave much for mistakes and wiggle room.Good luck if you go for it, but remember that the salary is only one part of the equation......

A lot more than my PITI costs combined.The condo charges a $250 sublet fee for renting out my unit; That would bring my total monthly expense over $2600; Based on what I researched I could get for rents in this area, not sure I can get $2600; Even if I could I would just be breaking even with no cash flow; Wont include amount needed for potential vacancy; The sublet fee kills my flexibilityDecision - Sell CondoProsWould probably get top dollar on sale of home selling now; if there is a downturn it can be MANY years before I can get the money I would be able to get now (anticipate $425k to $450k)Sell and use part of the money to buy new home for myself and/or use the money on alternate investment(s)Keep the money liquid for opportunities that come up in the next 1 to 2 yearsFree myself from the politics of the condo board and how the complex operates; A lot of the issues are financial in that over the years money has been collected and not well managed or spent which is why HOA fee is so high; this provides a level of inflexibility on managing expenses which I have limited control overConsDon’t have that much left on mortgage; selling now would mean investing elsewhere via new long term mortgage at todays higher interest rates (albeit at smaller mortgage amt since I would be able to put down a larger down pymt); Additionally, at todays market prices, I would not be able to get a unit like this one for the price I paid over 2 decades ago and for the interest rate I have nowI have been wanting to build a real-estate portfolio and my thought has been that this would be my 1st unit in that portfolio and I should keep it & build from there; Selling would mean starting from scratch instead of building; However is this Condo Unit really a good investment? 

It depends on the area but in most places it will be north of a decade. 

Been managing 15+ units under my families residential properties for almost a decade now.

I'm a buy-and-hold investor and I'm planning on holding on the property for decades, so instead of immediate resale value (which ADU doesn't compare very well with perhaps other rehab/flip projects), I care much more about long-term cash flow and long-term resale value.

I've vacationed in STRs for decades.

To make it worse, if it's a condo conversion you could hold it for a decade and then decide to do a condo conversion... it's short-term capital gains as you only owned the condos for under a year...that hit me hard...3.