The big risk items are setbacks zoning coverage and any structural work or foundation work that was done without engineering.

When I was managing a portfolio, my Airbnb and VRBO reps were both constantly pushing flexible cancellations, so I'm sure that is factored into their magic algorithm.

A DIY cost seg study may be the most cost effective, but it may have less tax benefits whereas an Engineered study will likely cost more than the DIY but should produce more potential tax benefits as it does a much deeper dive into the property.

To reduce your risk of audit, you want to be sure the company you select uses the IRS' preferred method, engineering-based.

Quote from @Steven Coulis: This thread is a bit old but the DIY/automated online options have evolved since, with some new players (including SegWize) entering the market...as well as some tech-enabled but still fully-engineered options like Segtax.I think the expansion of DIY options and the benefits of cost seg is great for investors of smaller properties, but I would highly suggest speaking with a tax advisor/CPA first to put together a plan and ensure you can actually use the additional depreciation first!

For more serious projects, we do an engineering-based cost seg with Cost Segregation Services. 

Tracy,From what we’re seeing across DSCR deals, exit flexibility is the priority — with rent assumptions a very close second.Most investors get in trouble not on the buy… but on the refinance.How we’re stress-testing deals right now:• Underwriting rents at today’s market, not pro forma or “once stabilized” numbers• Building in larger expense buffers (insurance, taxes, management, CapEx) so the DSCR still clears at higher rates• Modeling the take-out lender before closing, not after rehab, to avoid being over-capitalized in the dealA deal can cash flow and still be a bad DSCR exit if the loan sizing doesn’t work at refi terms.The strongest deals we’re seeing are the ones where investors reverse-engineer the exit first — then decide what purchase price and rehab the deal can actually support.That mindset alone has saved investors six figures more than once.

The ATG specifically mandates engineering principles for accurate and defensible studies.

A cost seg engineer can easily calculate your estimated potential benefits from your current depreciation schedule and provide you a quote, so you can determine if it is worth pursuing.  

I believe this is done through an algorithmic process based on time on market and potentially the previous bids.