With local home and land prices so expensive, I'd like to explore building a Tri or FourPlex on the back half of the lot. 

It will be more expensive for sure.There are some places you can get some deals on things delivered but they are often not the best quality.

ctype=...Meanwhile my 100k house I bought in cash 17 years ago sold for 325k but net only 237k after selling expenses, renovation and taxes.

We aim for a target cap rate, say 6%, aligning with our investment strategy.Here's an example: if a property yields $1.2 million in income and costs $10 million, resulting in a 6% cap rate.Then there's the adjusted going-in cap, factoring in potential changes in income or expenses.

At first they looked cheaper when I was checking them out, but then I realized they were actually MUCH more expensive than my current brokerage. 

The cheap homes have higher turnover, lower quality more problematic tenants and more expenses.

We both want to gain tax benefits so am wondering what I need to do to show the IRS that I am no 50% owner in order to write off expenses, depreciation benefits, etc.

Your position is that setting up a multi-member LLC is more expensive than a trust...lol

Comparing the average appreciation from one state to another is a fools errand  

Consider factors such as site preparation, ongoing maintenance, marketing expenses, and potential income from bookings.