Replaced floors and appliances, painted all the walls.

If you go over 3600 sf you will need to do a fire flow test and depending on the results may need put in sprinklers , although it doesn't sound like you will be getting that big.You need to park both units (duplex or main house+ADU), each unit needs 2 off street parking spaces for a duplex; main house needs 2 but an ADU only needs one and it doesn't need any if it is within 1/4 mile of an Imagine Austin Corridor (Burnet or W Anderson both are I believe).Also a duplex needs to have a shared wall that is at least half the length of the depth of the building (the wall can jog and zigzag, but the total length has to be >.5 of the overall depth front to back of the building).  

Partnered with a mentor who financed it, closed it in my name, we removed the junk, landscaped the property, had a professional arborist remove a tree hanging over the property, did some minor renovation work, and listed the property on the MLS.

The renovation consisted of all new interior and exterior paint, removal of popcorn ceiling, complete floor removal and install, complete kitchen remodel which included a wall removal and converting half of a closet into a pantry, complete master bath remodel, 2/3 remodel on guest bath, All new interior doors and hardware, new front door and hardware, new lighting fixtures, new landscaping, new paint for patio and front sidewalk, and pressure washed driveway.

Every wall, ceiling, floor, appliances inside and out, front and back of all doors, windows, screens, window treatments, lawn from every angle, siding, garage door open and closed, garage floor, driveway, mail box, etc.

Paint kitchen walls, ceilings, trims, moldingsIf the budget allows, you can go the extra mile and also do the following:6.

He should be out hanging with his friends, flirting with girls and doing 13 year old stuff.

Will need new HVAC, new electric, new plumbing, new walls/configuration, and possibly dig out to create duplex down (two-level unit) or 3rd legal unit. 

It had no flooring inside and bright lime green and orange walls from a teenage boy who used to live there without his parents.

@Niraj S. in addition to what others have mentioned, I'd add another important consideration:Does the driveway slope toward the house, retaining walls, or any other man-made structures?