It looks like you want to manage it well, but the enterprise level solutions (yardi, appfolio) are too expensive.

Identifying your desired level of effort and risk tolerance helps identify the appropriate investment for you. 

I was wondering how do you build a comfort level to purchase the property? 

I used the use this criteria for high level screening on sites: 600+ credit score, income must be 3 times monthly rent, 2 years of work history, no evictions, must provide at least 1 landlord reference.

Nice neighborhood and high rents.The upper level I was going to be able to increase the rent, just closing a weird second living room it has and convert it into a bedroom.

My wife and I have found a pretty awesome SFR with an ADU and potential to split the two levels into separate units and it's on the lake with no HOA.We definitely want to get this thing under contract, do about $35k in rehab over 3 months then get a cash out refi when it's renting out...we've looked into some of the basic options lease-to-own, subject to, owner financing...etc let's say all those are a no go...Without throwing the $150k as a 20% down payment on the $700k purchase price how can I structure this to be a viable solution?

I am considering the possibility of selling 4 duplexes in 4-6 months and looking in to something larger. Sale would be around $1.5M so that's the starting price for the next property. I like the idea of larger multifa...

Ultimately it's up to your comfort level. 

The good thing is BRRR's really work at any level.

Additionally, I'll be debt-free by then.I currently live in a suburb outside of Denver with my parents where real estate is quite expensive for entry-level homes.