I was thinking of putting in the lease that they'd need to pay for repairs to their hose if they get something stuck or if we know they damaged the vacuum (perhaps from sucking up used cat litter). 

Late /no rent payments, roommates might clash and you/PM have to deal with complaints, more likely to damage because lack of a sense of ownership.

Landlords,If you want free consultation time to have any of your properties roofs/gutters/siding inspected for damage cause by the elements reach out.

TONY MESA's videos were fantastic - His tips - Please Visit Every Other Night Dress Casually for ROI equations ..

I would just return the security deposit minus and damages. 

We haven't looked at the property to view any damages and what the rehab cost will be. 2.

In your case I would charge the tenant the full replacement price for all the lowers that are damaged and justify the cost based on you having to replace all the doors to match.Alternately you could charge 60% on all the doors but that is a aesthetics decision the tenant could fight regarding paying to replace all doors.For the tenant in the end the cost will likely be less depending on how many are damaged if you charge full replacement only on the lowers.

I'm stuck with the roof which has got few tree damages, roof repair costing me 1500 whereas roof replacement costing me 4000.What to decide?

Much more damage than I expected and I should not have purchased this home at all....but I only paid $4,000 for it and will have about $40,000 into it.  

Just saw a episode of Judge Judy.. similar situation.. and yes,, the insulation needs to come out. you could get additional quotes,  remove brush, trash from exterior, any tree limbs that touch building, get exterminator in to bait and trap. next will be holes thru the ceiling from the rats.. any holes or vantage points on roof they are gaining access from, by A/C unit or vents that are damaged.. they are getting in some how and food source is active enough to keep them.