Previous tenants had house dogs as do new tenants so I had no intention of replacing the carpet. 

We've been a little aggressive with our cap ex reserve on this house as we replaced all of the systems, so there shouldn't be any major expenses for a number of years. 

We made a profit last year selling a car my wife drove for 8 years, and the 10 year old van we replaced it with is up (according to Blue Book) almost 20% over what we paid.

Replacing the wood sill with a piece of granite or stone helps. 

Read your lease.Any filters that need regular maintenance/replacement should be specified in your lease.

As I would love to break in to Flipping  and flip this 3bd/ 1b house but  I can't  afford the 10 to  20  it Could cost right now so I  will do  a basic/nice  update replace only the carpet  in living and dining rooms,  No opening of walls ( if Flip kitchen would need to be done, it's a small and weird shaped kitchen) put new Kitchen cabinets back plash tile  floor and maybe re tile tub area in Bathroom and paint.

Should i replace every window?

Its easier to budget for when everything needs to be replaced.  

I threw the stove out and replaced it with a microwave and a undercounter 1/2 refrigerator and hoped whom ever rented it would eat out.  

Our goal for REI is not necessarily income replacement, but more for future planning (retirement is still 30 years away for us).