Worn flapper or fill valve in toilet, replacing a faucet cartridge, replacing CH/A filters, change fluorescent ballast, adjust screen doors and windows, flush hot water tank, replace faulty breakers, replace a circulation fan in a refridgerator, replace agitator dogs in a washer, change heating element or ignitor in an electric or gas clothes dryer, lubricating a ceiling fan, replace a p trap under any sink, replace any wind blown shingles, change any thermocouple in a gas appliance, do simple 110v flux core welding, do pvc/copper/pex/galv. plumbing, etc.If you don't know how to do those things yourself, someone else is going to make money off of you.  

After each puchase, I fixed up, inspected and replaced all old plumbling by new parts (e.g. shower cartridges, spout, faucets, chalking, all types of angle valves - toilet valve, bathsink valve, kitchen valve, washer valve-, water heater, plus others etc.) for all rentals.  

I do SFR only, as my rents are about 70-80% of a worn out duplex at the same price, tenant feel more at home, stay longer, and take better care of the places in general, I know thats not always the case, but by and large, thats been my experience, Rehb then with the least CapEx going forward, make them warm welcoming and reduce the stuff that is likely to break, for example, I pull any fans and put in new light fixtures, with LED Bulbs, I use Luxury Vinyl flooring throughout (no carpet) I replace faucets, and mixer valves(at least cartridges) and replace toilets, or at minimum fill valves and flappers, we also put in new switches and receptacles, we never do fridges with water and Ice, my tenants love their homes, they are clean fresh and comfortable. 

I'll buy the respirator cartridges!

I buy my printers on Amazon and refill ink/cartridges on supermediastore.com.

The way I would typically save:1: buy empty ink cartridges on ebay.

Is the printer cartridge old or running out of ink?

The XL black cartridge costs 36 bucks and does about 2,500 full size pages.

i have suggested in forums that Austin non-local landlords replace bath cartridges on new purchases...as we have hard water and it would likely save a repair call in the future...got shot down on that one.  

As far as the shower/tub issue, that could be a $5.00 knob or require a new stem or cartridge but is the tenant unable to get anything done on their own?