Do not continue on your own.For your next tenant, be sure you have strict screening requirements and do not waiver from those standards.

Your only option will be to find a job to supplement your diminishing ability to sustain your standard of living.The income must last throughout your lifetime.

What is your average booking lead time? 

Here’s a breakdown of some of the information you may need to provide for a cost segregation study.For existing buildings:List of equipment on the propertyProperty settlement stateAny appraisals or purchase/lease agreements Property maps or blueprintsSchedules, change orders or documents for future renovation plansSupporting documents for calculating real property book valuePrevious purchase price allocations that separated assets into their appropriate allocation and valuePast site inspections and photographsDocumentation that proves or records deterioration of assetsFor new construction:Contracts or contract paymentsLand and property sizeBlueprints of projectList of equipment involved or purchasedList of projected costs including costs for land developmentApplicable site inspectionsConstruction schedules and payment requestsPhotographs of completed assets or work in progressCost segregation specialists typically have an organized plan for the collection and analysis of the information provided.

If you do get someone who stays for an extended period you can remind them again after the booking. 

Lol, I'm  not sure i was very helpful, more anecdotal lol.I learned to estimate from other contractors many years ago.I found labor unit books from college bookstores.

But in reality you might just want to think about using a standard savings account And taking a hit from inflation on the cash because the delta from the higher interest account to the regular account is not really that much on small amounts.

I would suggest getting Dave Ramsey's book called The Total Money Makeover and read that.

This step by step process is all laid out in Scott Trench's book "Set for Life".

However, there isn't a standard form like a NAR lease agreement; it just needs to provide some general information.