I use excel to calculate costs and have it tailored to my investment strategy. 

I suggest reaching out to a mortgage broker who is familiar and comfortable with non-traditional financing methods, specifically tailored to investors to discuss. if you'd like a starting point -- try @Alex Bekeza.Hope this helps!

I think the approach of 3 months vacancy + big ticket item is a good starting foundation and then tailor it to fit my specific needs! 

Summer, this is a legal document tailored specifically to transactions where an agent is present.

We are considering converting to AppFolio or other more robust software that are more tailored to larger portfolios, but haven't been able to find if/which software companies provide this.

These ways include, but are not limited to:                      Using lists tailor made to accommodate your needs.

(I'm assuming your doing 50+ unit apartments)and if not, then that seems to explain why you can be more free spirited with deal analysis.OR, maybe your leads are more tailored to your liking than most.. leaving less room for outliers.. which seems like a valuable method, just be clear with your brokers and bird dogs, and you've got less time to waste on getting nitty gritty.. 

All that said, when I read all the 'getting started stuff' it seems tailored to a different audience than the one I'm apart of. 

Once you decipher the code, tailor it to your own situation and crush it.

Consult your CPA for specific guidance tailored to your unique circumstances.There may be another recourse.