I would need to do about 15 to 20k in updating, patching, paint, flooring, etc  to get it rent ready.  

As far as holes in the walls, it is unfortunate that some tenants use large nails to hang pictures and they make other holes in the walls for who knows why, but repairing even large holes 12" x 12" inches won't bust your piggy bank because we freshen every unit when a tenant moves with a coat of paint and if you are using a painter worth his weight in salt then he should be able to patch a few very large holes within 1 or 2 hours and the cost for materials should be no less than $30 to not one penny more than $50.You will just waste your time and aggravate yourself by feeling your are a victim and you have been violated.

We have a building that has a pretty rough roof, One section has been patched and I'm thinking we need to just replace the thing.

Allow me to clarify...I am doing the hard stuff: wiring, plumbing, windows and doors and wall patching....then cleaning and painting....which only leaves fixtures, cabinets...etc

Do a few touch ups to the unit (curb appeal, patch drywalls, sinks etc).

Joel,it all depends on how much stretching is required, most of the time I had to do patch up work along with stretching but I would say I paid close to 150-200$ for streching an 1200 sqft place generally.I have a guy who does a great job with carpet stretching and fix ups PM me if you need his contact info.

A contractor doesn't want to big on a drywall patch.

I have done  major renovation (no such think as basic fix up for a Victorian) on a dozen Historic homes, that had all been bypassed by other investors.You're dealing with +100 years of various owners patching over problems.

Where the roof leaked and was patched you also need to look in the crawl space and make sure there is no rot or mold on the beams between the ceiling and the roof. 

It looks like it will take about 150k to bring it up to its full glory and probably about 75k to patch and paint.