Why just convert tables when you can convert whole rental_statements? When you can verify whether your conversion is correct by reconciling inputs and outputs? When the data gets inserted directly into the financial database? And that data can be 'SELECT'ed later into a spreadsheet whenever you so desire.
My comment is not quite so facetious as it might appear. I feel your price:effect ratio is a bit too high. Especially if you want to have a subscription model. Most people have instances of one-off requirements for an app like yours. Those instances may not occur regularly enough to justify a monthly subscription. I wrote my app above purely for our internal use, but that could be rewritten by you and be used by many small-business landlords out there every month.
