The problem re size is that a "porch" awning covers a large range of sizes. Some are onky basically a small "airlock" over the door whilst others are not far short of a full sized awning (which can seem vast). If its of any help there are two of us and we have a 390 porch awning (that's 3.9 metres) which extends outwards 3.25m (it is an air awning so not realy suitable for what you want.
It's this one but it gives you an idea of how big it is when attached to a caravan (that caravan is 7.3m long)
That gives us plenty of room for a table and a couple of directors chairs to eat at and a couple of Lafuma type recliners, along with a bit if storage space.
If you are planning on being resident for an extended period, rather than visiting at weekends/the odd full week then I would suggest that a full sized awning would be more suitable.
Best bet is to find somewhere where there is a wide range of awnings erected. That way you can get a "feel" for the various sizes and see what would suit you.
One last comment " You don't get what yiu don't pay for!"