In my situation, a professional clean up crew repaired everything and also didn't find any mold inside of walls before starting the cleanup and new flooring and dry walls were installed and it was over ten years ago.

Seems cut and dry that with limited exceptions JADU can require owner occupancy. 

Many agents will place the first applicant with the necessary funds, take their commission and leave you high & dry with a bad tenant.YOU SHOULD DO YOUR OWN SCREENINGS! 

I am a first time real estate investor looking the following property : https://www.redfin.com/OR/Forest-Grove/2418-Cedar-Cir-97116/...its a pretty large duplex in Forest Grove OR,  the trick is though, its on a lot zoned for a 4 plex so I am lookinginto house hacking, converting into a triplex, then living in one unit while renting out the remaining two unitsThe left garage has been converted to living space, with a living room, half bath, a laundry room with a sink and some counters/cupboards and a bedroom, it is a part of what was an existing 3bd unitIf I were to acquire the asset, I would first attempt to convert that space into its own unit The line items as I see (be in mind, I am totally new to this) would be to >put up dry wall where the door to the rest of the house is,>add a shower to the half bathroom >install a water heater in the adjacent 3bd unit> install a kitchen in the laundry room, (stove , oven , sink, counter space)>add a shower to the half bath Assuming I can convert it to a 3plex, I could at-least cash flow on my investment after I leave My plan would be to put minimum down payment of 3.5% (FHA loan) that way I can have a decent amount of capital free to do the renovationsThe only concern is when I crunch the numbers to get my ROI, I have no idea how much its going to cost to convert the additional living space to a third unitAny experienced investors here know how I can estimate this before I try to make an offer?

Soil type, adjacent land and what they have on them (spraying chemicals or not).

The kitchen is what's sold me in my first house and it'd a great lay out in my current house.My next house I'll be a bit more specific - bigger deeper sinks, pasta faucet even if I only use it once a yesr for a big jug of summer iced tea lol and a dishwasher, walk in pantry are on my check list.I feel other amenities like skylights or big windows, cellars for dry storage would be cool too but I'm not really a big baker or canner lol.Now it's got me thinking - imagine a hidden island?

Those developers pray long enough while building out the building that the tenant will open and they can sell it off before taking a bath on it.The small to medium franchisees eventually if the have trouble get bought out by a Private Equity group that runs them like sh*t and makes their money back and sucks any remaining profit dry before they close or ask landlord for rent reduction.That's what 20 years experience teaches you versus buyers just looking at a cap rate thinking something is a good deal.

Quads on a septic system is going to be a major expense and you should expect to pump it out every 2 years or so, so it needs a man hole cover.If it is going to be septic be SURE you have sufficient soil quality for your drain field, you will want lots of sand.

It might be a good idea to tie the site up as long as you can to get some soil testing and at least some preliminary drawings done by the civil engineer to see exactly what the site work costs will be. 

A current tenant has damaged the rental property beyond the normal wear & tear. (3 by 6-foot hole in dry wall; Garage access door complete broken off with damage door frame, the main entrance door way frame is broken and need to be replace, damage to the rear entrance door frame as well).