On both units, I've installed sediment filters, industrial strength water softeners (not the cheapo ones from Home Depot), and reverse osmosis systems.

Usually big-tickets items (roof, furnace, etc.) have really good rates within financing thru company that installed them.I also add extra personal touch items yearly, just before giving any rent increases

I like to have a set of pics from before moving and to compare ... they may remove towel bars, etc and you may forget that there used to be a towel bar there ... until the next tenant asks you why there is no towel bar and requests that you install one.    

You could add LED lighting installed hidden away under the cabinets, this provides a great look, extra light for working in the kitchen and adds value at a low cost.If you're looking for new flooring, possibly look into buying bamboo floors as they're popular currently and thus are often over stocked and can be bought from a company like lumber liquidator for around 1/ per sqft.This sink fixture is often the only thing needed for the sink to look new, getting one with a hands free feature would be an added cost item.Another low cost-high reward option would be replacing the counter top and repaint the counters and cabinets. 

I like using natural stone in my flips, and that doubles the installation price almost instantly.

I give my tenants choices all the time, in fact at lease anniversary time they can choose 1, 2, 3 year lease, new window air conditioners, ceiling fans, paint….. but I show them their rent will increase based on the improvement option they choose.AC is a big one: so I spend $150.00 on a window shaker, divide that by 12, add a service charge for the install… and viola’ we have a new number to add to the rent.

Let’s do the math: I’ve given them $250.00 in five years, oh yea, I put new carpet in the living room because it was old when they moved in – maybe $400.00 (installed).They in return have paid me a couple of late charges and in addition $54,000.00 in rent alone.All on a house we paid $45,000.00 for 9 years ago.

If we need to re-side the property, we'll install new siding over the old asbestos siding, and it's perfectly fine.

After I fix it up and get my tenants installed I want to get a mortgage and pull most of my cash out. 

We are thinking about installing AC since a lot of renters ask for it and we feel it may be a good addition to the property in the long run.