But there is concern of a barbell economy. 

Then you got laid off and now you want to blow what little money you've saved on something most people lose money on their first time, just as the economy heads into a recession?

Quite often, new home construction is the result of new residents moving in who are middle class or wealthier, attracted by jobs, a healthy local economy, or other amenities as they leave nearby or far away areas for greener pastures.

This is an open question... what are all of your experiences in the share economy platforms?

Assuming IRA is invested in stocks, the remaining $ in IRA will grow 10-15% for a few years (as long as economy is good). if you are making 45k in NJ, it means you are underemployed.

As the economy and consumer confidence continues to improve, rates will increase. 

Is there a current thought of fixed vs variable in the economy?

I would go with whichever one I found the better deal on first.In terms of vacancy a 4plex would be better for the economies of scale.Are you planning to house-hack or is this purely an investment?

1. little to no economies of scale.

@Shane Gaboury I would personally stay away from any condo investment because the economies of scale (only 1 - 3 doors), the special assessments that you have no control over and this is a speculation play.