If not, how do you plan to attract tenants? 

It is a knish market and to succeed you must have a well known name and reputation to attract the elite that will pay based only on being able to drop names among their world of elites. 

I would be using the existing structure for storage for an existing business (which could pay rent to my RE entity), and hopefully building on the land in the long run once the neighborhood becomes more attractive.

We are going to inform them of the renovation along with the rent price increasing before they sign the six month lease.

Increase the character count for the PROPERTY SALES DESCRIPTION field. 

Trying to understand how to attract our vacation rental investment owners.

I would raise there rent to full market (they are not good enough tenants to deserve a reduced rent) and mention the filth being unacceptable and liable to attract insect/rodent infestations.

Even if the roof repair is covered by insurance, is it best to avoid it for smaller things to avoid increased insurance premiums?

I would like to increase it if possible.

I have seen an investor pay 8k in closing costs to pull out 20k equity, so he only netted 12k and a $700 a month increase in payment.