Maintaining proper records is essential in case of an audit, as it allows you to justify and substantiate your deductions and effectively defend your position if questioned by the IRS.

Conservatorships can get audited or questioned later, so written records will keep you protected.Lastly, don’t take your mom’s resistance personally — that’s super common in conservatorship cases.

Does anyone have personal experience with specific scrutiny of a logbook during an audit?

We have done reg d 506b, reg d 506c and reg a+ offeringsI would not do a 506b again but definitely a time and place506c allows for general solicititation and accredited investors and is where most goreg a+ allows for non accredited investors but has much higher cost structure - would only do it if raising $25M or more and you must have a robust team (cannot do it alone like a 506c) as you need someone to deal with non accredited investors questions as well as a rockstar accountant to do audited financials - outsourcing it can be nightmare. 

Clearly the more stays,  the more defensible in an audit. 

(forgetting to log, categorizing activities, proof for audit, etc.)I’m even considering building a dedicated software/app that makes this easier.Before I dive into it, I’d love to know if there's a real demand and what features would be must-have vs. nice-to-have?

Each property is so different that that is why a good engineering based study with on-site property review is the IRS' preferred methodology and keeps you out of IRS audit territory. 

Watch for vacancy and expense assumptions — most banks will “normalize” both, which can impact proceeds.Due diligence – Get a full lease audit and T-12 tie-out.

The shown bookings won't reflect the actual bookings and it could be grounds for an audit.

On top of that, short-term rentals and long-term rentals follow different depreciation rules, so it’s easy to miscalculate and miss out on deductions or trigger audit risks.