The downside is there is only one electric meter/panel for the whole house and there would be one bill for both units which includes heating/Central AC/electricity and so forth.

If you're in the right area the upside potential is far greater than the downside risk But bottom line do your due diligence and work with a purveyor that knows what they're doing.

Only downside is you may have to provide the unit furnished to attract those kind of guests. 

The downside is there is a lot of places to make mistakes that cost significant money.Getting started, I would be looking at stale MLS listings.  

There is still some significant upside here but at 275-  downsides start to loom a bit larger. 

If I am unable to find a buyer, I will at least make the listing side commission, so I virtually have no downside risk.3.

I will only pay interest on funds as they are drawn and can pay them back anytime during the loan term.A potential downside is the rates are variable.  

As for the down side is when you try to qualify for a loan and you need that extra income from your ADU qualify, lenders would still appraise it as a single family meaning they would use market comparable rents for one single rent vs a house with a legal ADU which could increase your borrowing power up to $10k or more.

That’s their downside, what’s the upside to taking your offer over being done?

These people either 1) Have money sitting around with nothing to do and are afraid of the market with its volatility 2) Just use arbitrage and borrow at like 4% and loan to you at like 15% and keep the spread with no downside.