Keep in mind depending on your location u could be at peak market values, don't over leverage without capital to burn in hard times, also consider starting the conversation w the seller about a deal in the future...u might just see a dip in economy/mkt and reap the rewards of patience a few months down the line but I understand striking while the iron is hot too.

Do you think even if the cape-cod rental is left vacant during the off peak season it is going to be profitable?

The down-side right now is the market is at a peak through out all of Macomb County.

Not a direct answer to your question, but an FYI before you get too far into this if you don't know already:Multiple ADUs on one property = no Fannie loan = bye bye resale value & ability to refinance (excluding HML).Whatever you call it, you will want to make it easy/quick to make that other accessory unit not exist prior to listing it, or having it appraised for a refi.

However, interest rates continue to fall (which is good) BUT it seems the housing market generally may have peaked, which could impact my appraisal value if I wait. 

Hello BP community-I've been an avid listener to this podcast ever since my interest in real estate peaked last year.

As @Tyler Work said, people are looking for unique experience, and with all the TV shows, the "tiny home craze" is at peaks, even though everyone interested would probably never do it themselves (but they can live vicariously for a few nights through yours!

Even though I knew my partners before ever investing with them (friends and family) I only peaked their interest during normal conversations about "what are you up to"  and them showing interest in what I was doing.  

So don't be expecting to stay in at peak season, or any holidays, because that's all your earnings. 

The national median home value is now $217,300, an increase of 8.3% on the year and 8.4% above the bubble-era peak.