I've been told that prospective buyers will be unable to get bank financing if the sewer line is damaged. 

I'm a Referral Agent with Coldwell Banker's National Real Estate Referral Group and I interview my prospects to better understand their objectives, their budget, their geographic and other preferences, as well as their overall perspective.   

Also, if vacancies are coming up, and there are situations like this, do you think any landlord who is not very certain will rent to a prospective tenant w/a low or average FICA score?

i do think the lenders are motivated to help as they know the prospect of selling for what is owed is a bit lower right now.

Likewise, downpayment assistance programs don't permit renovations loans. 

Agents and landlords can provide a virtual walkthrough experience to prospective clients or tenants.

Sam, I am not sure about your area but in my area, prospective tenants are still looking for places to rent. 

I am assuming I will have to remove part of the ceiling above the kitchen to access the drain lines to the bathtub and bathroom sink.Do I need to acquire permits for this job and what would be the best way to go about replacing the whole cast iron pipe from the roof down to the crawl space.

They have pulled electrical and plumbing permits for the bathroom, but are saying that a building permit is not needed since the two spaces are already framed and existing.I tend to disagree, as based on my research the county (Loundoun Co in No VA) wants a building permit whenever a room is finished or drywall goes up. 

Also, to provide full disclosure, I would inform all the prospective tenants that the nurse did test positive but now is negative to ease any issues.