They are both quick ways to compare opportunities within the same market, but trying to track a relationship seems... not useful at all. 

Obviously directly comparing flipping to buy and hold is not applicable in all situations.

One duplex through the other day that looks promising (still a low 5% cap but that seems to be amazing compared to all the other properties ive been sifting through). 

Yes, the higher the rent to value ratio, the better, but some of my most reliable cash flow producing props have a ratio lower than 1%.

He's helped a lot of my house hack clients navigate comparing conventional, FHA, Home Possible as resources for only putting 3.5-5% down on an owner occupy multifamily.  

Compared to an IRA, Solo 401k contribution limits are roughly ten times higher.There is no custodial requirement for the 401k.You don't need the additional expense and administration of an LLC to have checkbook control.There is a built in-Roth component whereas IRAs are either traditional or Roth, not both.A spouse can also participate in the same Solo 401k plan.The Solo 401k has additional tax benefits over an IRA when investing into real estate using leverage.You can borrow from a 401k, but not an IRABoth C-Corps and LLCs can adopt a Solo 401k.

I have not discussed comparable building specs with a traditional builder, yet. 

Also what does everyone think of using epoxy paint in the floors compared to laminate?

How hard is to get tenants for house that is relatively far from public transportation compare to one that is very close?

I built 50 homes in Gresham last few years and that was a breeze compared.. and we just bought 90 lots in Canby and they are a joy to work with.