Sorry no I meant number as in how many would you want at maximum. That is if you're only planning to need a driver's license it's a lot cheaper than if you think you'll need a firearms license, a concealed carry license, a driver's license, an occult investigators license (to explain the guns). I'm assuming your just straight face not a mage so we can rule out magic license and combat magic license and the various other transport options e g. Pilot's license. Need to know how many and what because you don't necessarily need all of the licenses for all the Sins e.g. No firearms license for your legitimate sin.
Hmmm well as I said I feel you need at least 2 as a runner. Hmmm wanting to spend as little as possible rather than having a set budget is s bit tricky I think I'll leave it up to you to decide and just post some generalities to choose from. Give me a little bit to sort this out.
EDIT
ok I'd start off by looking at these for a face.
R4 Legitimate SIN (can also be a national or corporate sin it you took the negative quality)
This is your general living one legal, legitimate, tons of spam and try to avoid licenses that could be problematic I.E. Things for work. R4 is the minimum I'd advise R6 myself if you can afford it.I'd also advise having a spare clean one of these secured in a safehouse to start over with if it all goes wrong.
R3 semi-legitimate Face SIN
Again R3 is the minimum I'd suggest R4 to R6. Self defense licenses e.g. Firearms/concealed carry. This is the one you use to meet with clients kept at a high level because you'll need to get into clubs and other high class establishments with good security if you do well.May need to be burned if your double crossed.
R3 illegitimate Running SIN
Again R3 minimum I'd advise R6. This is the sin you use on runs and burn if you feel it's getting too hot or well known. Has the full range of licenses needed for your job. Kept separate from your face SIN because that identity will be known to the client and if they're planning a double cross you don't want them passing on your identity (try to use this for gathering info)
R1 burn SIN'S
Three r1 use and burn sins for emergency use, as the face there's a higher chance you may need a backup after using one, minimum self defense licenses. Two kept available and one in a bug out bag.
Licenses
All these should be at the level of the associated SIN but I can't say what you'd need without knowing more about the character do they drive, have a handgun/shotgun/knife, etc.
The minimum you should have as a runner in my opinion is a legitimate living sin, an illegitimate Running SIN and a emergency burn sin to get clear and I'd strongly advise a back up clean sin to run too..