Real estate's "gross rent multiplier" is Wall Street's "sales to revenue",  "cap rate" is roughly "P/E ratio".When evaluating markets and investments I tend to start with GRM (or lazily the 1% rule), then attempt to return a cap rate based on assumptions about costs, then I work my way to multiple years of projections (assumptions about inflation, amortization, tax benefits, etc), and if I am partnering with one of my smart friends I have to pull up an IRR (internal rate of return).I also look at regional employment levels, median income to rent ratio in the zip code etc. 

Some lenders might evaluate the same deal differently.

To determine the quality of a property requires to evaluate all of its return as well as potential return.  

Other than just going in and looking at what's on Redfin.com and using the tools on here to evaluate a deal, is there anything else I can do on here?

You can evaluate the additional cost and payback time as if you were paying for heat to get a handle on it but the jump to most efficient is probably not worth it in your situation.

Just like when evaluating a potential purchase you should be performing the same due diligence with rents.

The income approach might also be used, evaluating the potential rental income the ADU could generate.

Assess Your Goals and Current Structure: Beyond replacing your handyman team, it’s important to evaluate your portfolio’s current management framework and clarify your long-term objectives.How are responsibilities currently divided among you and any co-owners or family members?

When it comes to turnkey investments you are paying for convenience essentially you are approaching it like a stock or paper asset when it is very much not... meaning that at some point it needs to be actively managed and evaluated and etc., etc., etc. for example finding cash flowing investment properties which meet your ROI goal of 9% is NOT HARD heck almost every state (and likely every state) has a market which will achieve that but what does 9% mean without a dollar value if 9% is = to $200 or more okay that’s okay but if 9% means $25/mo. or alternatively if 50% ROI means $25/mo. doesn’t really matter much since although labor differs from area to area it doesn’t differ that much and also doesn’t really leave much room for error — so your minimum accepted ROI should also be couple within a minimum accepted $$ value (cash flow) and other minimums as well (i.e. min. equity, property types, property classes, etc.)Lastly as I mentioned achieving a 9% ROI is not hard and is achievable in every state; the HARDER part is to 1) achieve that AND 2) achieve 10-20% min.equity on the buy in or ARV AND 3) meeting your min. $ value AND 4) buying in a good/stable neighborhood/market AND 5) buying with some type of upside AND 6) etc. etc. etc. —- Again I’m not saying you have to do these things; it all depends what type of investor you are and what you are looking for however it is important to understand that if you shift the responsibility of either identifying the invest property or managing or any other aspect there WILL be a trade off — in this case the turnkey company has delivered on your goal of 8-9% ROI (projected... so TBC) and in return you have traded some of the other benefits of investing in RE for the convenience of not having to do much more than to look over the properties they have sent you and funding it from the comfort of your home, office, etc. ... again if this is the goal then you are on point but if the goal is to also partake in ALL of the other benefits of RE then you should understand that and not be surprised that it’s not a ‘stellar’ investment that checks all the boxes.

How do they evaluate deals?