You've already got some good recommendations.
If this is a first jointer and planer for you I would suggest buying a used 6 inch jointer and a used or new 12.5 or 13 inch planer. Used 6 inch jointer sales come up a lot as someone upgrades to an 8 inch or larger jointer. You can get good bargains going this route.
Used lunchbox planers 12.5 - 13 inch come along (less frequently than jointers I think) but new prices are not terribly high.
It will do you no harm to learn to use a 6 inch jointer and lunchbox planer. The skills learned will benefit you if you decide to upgrade later, either to larger stationary jointer and stationary planer or a nice combo unit. You will learn how to read grain, how to visualize the resultant plane you desire when face jointing stock, how to handle heavy stock on the planer and avoid/minimize snipe. You will learn to change blades - including adjusting knife heights, check bed alignments, etc. Once you gain this skill, you will know when you need to upgrade.
Several folks on the forum have some very nice, well-built combo machines - top notch stuff. I just don't know that I would recommend a combo machine for an initial purchase, unless you've been doing this hobby for quite a while and know you will stick with it and know the combo machine fits your style. My gut feeling is that you will lose more money trying to sell a USED combo machine that you purchased at NEW cost than you would selling a USED 6 inch jointer and lunchbox planer that you paid "USED" prices for.
I am NOT advocating buying a flimsy benchtop jointer - buy some SOLID iron. Once you learn to make flat, square stock with the less expensive MACHINERY you can make an informed decision on future upgrades and sell your old machinery for minimal or no loss.
My $.02.
Chuck