Is there an opportunity to upgrade the interiors in order to raise rents?

If your plan is to upgrade the triplex and get a better caliber of tenant in there, well, a registered sex offender might scare folks away if they hear about it. 

As long as you can manage right, you keep pressure on them and treat them right then it all works out just fine.As I'm about to get into long term rentals (I'm putting my first offer on 4 family tomorrow) my biggest fear is to have to be committed to go to my rental property at 12am and have to fix broken sink or clogged toilet.... 

Tenant and SFH resale do not go hand in hand.Your best option is to set it up now for tenants as I suggest and then do another reno to upgrade for sale.....possibly stone, hardwood and tile to maximise profits when you sell assuming they are appropriate for your market.

Maybe get somebody to re-lay the broken bricks and coat with a sealant.

What you wrote is exactly how I've been planning out my real estate journey in my head, by doing a house hack, becoming debt free and flipping broken cars in the beginning of my journey.

I am only looking for something small  - less than $10k for minor plumbing issue and electric upgrade. 

But now I am able to bump up rents $100 to $200 with very minimal interior upgrades between turns.

The person doing the work should provide a written invoice with materials and labor broken out.

When banks stop lending to other banks, because they cannot determine with any level of confidence which assets on balance sheets are really worth something, and how much, OK that is not a cyclical market correction -- that is a broken market system.There was a time in late 2008 when some big names like CAT and Deere and Honda and Toyota and others like them were unable to obtain debt funding for their financial services captives for a period of several weeks.