If you already have iOS apps making money, I'd say the easiest path to additional revenue would be iOS tutorials/screen casts/code examples. There's a market for this, I've paid for such things several times. Take a look at: http://www.raywenderlich.com/store/ios-apprentice

Get a Stripe account and a copy of ScreenFlow. Pick 5 new iOS 5 features and make a tutorial + example app. Then spin up a little Rails/Django app to take $10 in and spit out a .zip file.

Interesting can you share the apps that you have already built?

Second this :)

third it!

Fourth it

Fifth it ;)

Sixth it :D

"What is the easiest way to get a web app up and running that would generate $10 a day?"

Solve a problem.

Take a close look at stable, non-tech industries to figure out a common problem that a number of businesses inside of them share. Ensure that your solution will save / earn the company more than $10 a day.

Its most likely that you would need to build at least 20-30 apps that some of them will make 1 or 2$ a day.

I would recommend to focus on 1 app only and put all your coding, marketing, promoting and design chips in this app.

First of all, congratulations on building a few apps that are generating $10/day - some people have never made t this far and have given up before they have reached this point.

With regards, to building more apps, in my opinion it is easier to build 1 app/site that makes $100/day than it is to create, manage, operate 10 apps/sites that make $10 each per day however, this is hard to say without knowing your existing apps.

There are several factors for the fact that 1 is better than 10+ in my opinion including, the fact that they will all require maintenance, management, promotion, support etc and this is time consuming especially, if you are operating 10+ sites/apps. I have seen people attempt to do this and they have managed to a certain point but then it becomes problematic, even on small scales with 100 sites producing $1 each/ day and have eventually merged them all into one since, it is far easier to manage 1 bigger site/app.

However, if you are really determined to build 10 apps that produce $10 each/day then there are loads of ways of doing this but, it depends which route you would rather go down i.e. FREE apps which are monetized with ads & even in-app purchases or PAID apps which can also be monetized with in-app purchases.

Likewise, you should have a look at PhoneGap - http://phonegap.com/ with regards to a framework etc since, you can build and easily deploy your app to multiple platforms (increasing your revenue streams) since it would be easier for you to launch your existing apps onto Android, Windows Platform and BlackBerry's etc.

Again, without knowing your existing apps, I can't really say if you should solely focus on scaling these up to producing more revenue and expanding them or launching a "bigger" type of app which can make $100+ per day since, whilst I have highlighted in my opinion that it is easier to have one core focus there are also certain aspects which can limit their expansion strategies.