Seller financing, in its simplest form, is a note for a free an clear property that the seller carries instead of the bank.

Your input is absolutely crucial – it's the secret ingredient to REI's success. 

This seems the simplest, but will it cause issues down the road when I goto cash out refinance on the same property once casita is built with heloc money? 

It's been one of the simplest and most profitable investments in my RE portfolio.

This is the simplest method, but it also means your tenants are more likely to abuse the utilities by leaving windows open with the heat or A/C running, leaving lights on, ignoring the toilet that constantly flushes on its own, etc.3.

More often than not, I see out of state firms make errors on anything but the very simplest NH situation (heck, a lot of NH tax preparers also get it wrong). 

My personal experience as a successful real estate investor has demonstrated that with the correct mindset, effective strategies, and strong determination, anyone can achieve impressive results.Consistency is the key ingredient that keeps my investment strategy strong and steady!

When these payees are shared across all projects, it's a mess tracking what expense goes to which property.What's the simplest/easiest way to do this?

Glass block and tile are probably the simplest solution.

This is the simplest method, but it also means your tenants are more likely to abuse the utilities by leaving windows open with the heat or A/C running, leaving lights on, ignoring the toilet that constantly flushes on its own, etc.3.