Will this require the septic tank to be replaced with a larger one to meet code?

What is monthly rate if they have it?

Rather than asking non potential customers in here you can get a better result from potential customers, As well as tour of the competition.While you are there, maybe take some pics, and make a written record of rental rates and what features they have for that price.In a nutshell, become an expert on this specific investment in your local area and neighborhood, in order to try to reduce the risk of just guessing.Good Luck! 

In the Wayne County Michigan area for a duplex that's renovated, what are cap rates in that area an investor would seem to look for?

Rates are high right now, so unless you have something immediately ready it might make more sense to hold.

Does HELOC and other home equity financing methods work in the current high interest rate environment?

Rates can really vary depending on the relationship 

Nj is very cash demanding unfortunately and my thought process is to try and find an assumption mortgage to lock in at a low intrest rate and finance the equity the seller is looking for to move.

What are the differences in tax rates if I hold the property for less than one year versus more than one year?

Hoping to meet like-minded investors as building with a team is the best way!