How much $ to spend udating to raise rents by $300

[Joseph L.]

Hey guys,
Just purchased my first Condo property and wanted to get some thoughts about putting money in and upgrading.
Currently the unit is rented for $900 and they know this is under under market value so they are willing to go up to $950-$1000.  Lets say $950 to be safe. The unit is in fine working condition and does not need anything new, but the problem being it has not been updated since it was boughtand looks like its 1979 when you walk in there.  Another investor in the area with the same 2 units is renting out for $1250 each but they have been remodeled.
Main things that need get remolded are 
1. patio deck needs new roof and floor boards.  size is 8x8 was quoted $600 for roof and thought I could just go buy wood at lowes and do floor myself and apply finish/coating.
2. Carpet in upper level master suite is old and blue.  Around $400 sqft including open loft and halway and stairs.  Was thiniking of replacing with carpet or with fake wood floors, would install myself but haven't checked around prices. - I am assuming that normally carpeted stairs are wood underneath?  Can this just be painted to match hallway to look nice if I decide to go with laminiate wood or carpet?
3. Carpet in anothe bedroom downstairs is also blue around 10x12 room.  Will replace with same as above(carpet or fake wood), don't know if thats tacky/wise to do.
Now things that could use updating
1. the cabinets and counter top kitchen and two bathrooms (good workign condition but is it better to buy used/new or can they be refinished/painted?)
2. Tile throught bottom floor in dinning room/living room guess I could upgrade to carpet/wood but they don't seem too bad looking they are the big size tile's like foot long.
3. Loft in upper level could be extended out to create additional 6x8 space was quoted $600 for basic floor and railing and to add 1 outlet.
4. Can screen in patio as my friend might give me his hot tub and this is florida so  lots of bugs, also previous owner loved plants/trees so very jungle looking in backyard this will be cleaned up by me.
So basically my question is to raise rents by ~$250-300 which I know is possible in this area how much would you be willing to put in a place to achieve this? If I can get $300 more a month it would be worth it to put in $3-5K with just about all of it going towards supplies and not labor?  Do you think this is possible, I would do all the work I can and my gf's dad is a contractor so he would help me with the hard stuff. 
 Also what type of payback period do you guys look for in a place? I am looking around 5.9yrs for my payback = Total inital investment if I make no changes at all to the place, 75% in financed.