Work w/an STR savvy buyer's agent to ascertain that info.

Since you're unlikely to be reading the paper, I will soon have a default judgment against you, and by the time you realize it, you may no longer own the property you thought you did... thanks to your land trust.If you actually want privacy and asset protection from the inside as well as the outside;1) use a series LLC for each property, making sure to draft an operating agreement for each series, open a bank account for each series, have separate books for each series, and never commingle funds from each series.2) have the series LLC owned (100% membership interest) by an intentionally defective grantor trust (IDGT) with no ascertainable standard for distributions (no HELMS), a bank or trust company (preferably in South Dakota) as trustee (starts at $2,500/year), a non-related (non-family) trust protector with discretionary veto powers over distributions, IRC § 541 provisions so it withstands federal bankruptcy, and many other details which are too lengthy and technical in nature to expound upon here.As long as you have a $1M or $2M umbrella policy, you may be able to get away without having item #2, above.

But, I was warned by the building inspector that, in some cases, the inspector will not approve work previously done without a permit, especially if he/she cannot reasonably see or ascertain how the unpermitted work was done. 

It is your/your Agent's responsibility to perform "Due Diligence" and ascertain all of the facts; clear all contingencies; obtain needed documentation such as rent rolls, tenant ledgers, estoppel letters confirming terms and SD; existing agreements, etc.

@Russell Brazil, my contract says "If Purchaser* defaults hereunder, Seller’s sole remedy shall be to receive and retain the Downpayment as liquidated damages, it being agreed that Seller’s damages in case of Purchaser’s *default might be impossible to ascertain and that the Downpayment constitutes a fair and reasonable amount of damages under the circumstances and is not a penalty." 

A lender will require, and most likely order their own market study to determine if more units are needed, ascertain the absorption rate, and see what sort of units (private pay, medicare, medicaid, VA, memory care, etc.) are needed.

Just because a beam is charred doesn't necessarily mean it needs to be replaced, but you will have to check local code and maybe speak with your building inspector to ascertain what will pass. 

“college student rental listings” with multiple students living in the units, how can I ascertain the validity of these numbers??

Police were called in two cases but person fled,  license numbers were noted and it was ascertained that they were indeed former owners,  but not much legally could be done.  

You need to accurately ascertain the monthly costs.