Hi, I always enjoy seeing someone just go for it, stick to the scenario you intend with and yes "some" amount of photoshop can be used to acheive this
type of render, but autocad can produce some pretty photo realistic images if you just work at learing to render in general, if using 2015 then you still have mental ray and to get the benefits out of it you will need a high core computer as mental ray in autocad "WILL" recognize the amount of cores you have, even with 3ds max you still will get the same results in time of render, (3dsmax save you about 3 hours) wether you use GPU rendering or cores, it just takes forever to get a decent quality no matter what program you use. You will set it to render and come back in the morning, or do what i do and start at morning so you can monitor the process-in case of power failures, not enough ram for the model, or the model just has too many poly's in it. I personally wouldnt go over 70 meg. For this rendering image you have shown, i know the image and it is actually all fake, the sun/lighting in the render has been modifed in photoshop, hence the glare off of the grass and long grass driectly in front of the house. the glare spots priginally started smaller but can be greatly increased and even color changed in photoshop. I do it all the time. The blades of grass in teh front have been specifically place to simulate that they are populted everywhere and specifically for this camera shot on a hill (not only that but they too are way too flat of a color and dont show differences in color along the blade of grass. The trees are totally the same with the resemblance of what looks to be fruit, but that type of tree doesnt blossem, bright shiny pine cones or fruit for that matter, it was an accident form the light adjustments created from glare when rendered. rapid render does use light based enviroments but again get ready to wait, and there is an inherent problem with noise-(speckling of light across the finished result) in the render engine and will take a decent amount of test renders with something basic before you go for it. You could easily create this with ACA2015/RPC archvision plants.
Create the grass your self with a surface and modfiy with nurbs to get some different bends out of a few of them and plant no more than 300 or the drawing will slow to a crawl, (which is one of the benefits of 3dsmax) no real need to worry about moving around the model due to it being about to handle a higher poly count. but if you do it right you will turn off/freeze the grass and/or create it last and keep it off/frozen until time to render. even create a test drawing to get those balde right before inserting them into the file. The ground of the landscape is again just a surface modifed by nurbs set
it to a soil material, and plat the trees appropriately in height and scale in the hillside. the house is built 1st and model the land around and or in another drawing and insert later. The render was done later in the day and will allow you to play with contrast and brightness giving you that realistic feel even before you go to a photo editing program. Look up how to render in autocad in google and follow the steps with both James smell, and David Koch so you can understand the basics of using mental ray, and it is actually a great platform to launch from to begin to use other renders, as settings might get more complex but you will understand how light works.
Good Luck! and ive left a few example of in-model planting of landscapes for renders.
none were modified yet in a photo editing program, yet