Hard to give specific advice without knowing what the app is. If you’re interested in going down the sales route I can assist as I have sold several apps and developed 100s for clients.
On the revenue side, I am assuming your already tried a freemium model with in app purchase as well as ad supported? Do you capture users email address? Are you utilizing push notifications properly? How many DAUs?

Hard to define a budget or timeframe without knowing the scope of the project.
It might be better to invest in a contractor UI/UX designer to create screens that will bring your app idea to life visually. Then you can use these wire frames to communicate your idea to a development company or a contractor to get budget and time frame.

I've been running a mobile app development company for the last 6 years. We've found the most reliable option is AWS (Amazon). Its got lots of options for scalability, load balancing, server alerts etc.
It really all depends how quickly you scale, even when you get out of BETA, you may still be fine for a short while.
However, if you are planning to do a large advertising/marketing push, I would make sure you are on Amazon before doing so.

I've ran a mobile app development company for the last 6 years. My team has developed many apps for entrepreneurs and startups, I am frequently asked this question.

First understand that startups are 10% idea and 80% execution. With limited budget and/or time, I would suggest to do your best to define the requirements of your app idea, mock up the screens to best of your ability (see: basamiq.com or mockingbot.com).

Next, after your idea is minimally defined, bounce it off of as many people (that are not friends or family, they are biased) as you can to determine if your solution to your perceived problem works.

In terms of getting investors, start working on a 10-12 pitch deck. See Guy Kawasaki's template: http://guykawasaki.com/the-only-10-slides-you-need-in-your-pitch/

Good luck!

I've been running an app development company for the last 6 years. Its good that you are even aware of the difference because many people don't. Going native is always best for performance reasons (there's lots written about that so I wont go into the pros/cons) and access to core OS APIs. For a startup, there is no reason for the need to be on Android and iOS at launch, which is typically the main argument for going hybrid (one code base, both platforms, lower cost etc).

I would say go native, minimal MVP for your startup and iterate on the features once you have a decent number of users on your app. This way you are building a quality product from the start.

If I have a better idea of your app and what your trying to accomplish I may be able to assist further. Good luck!

I've been running an app development company for the last 6 years and come across this question frequently.
"Proven" means you have put your MVP out there, spent a little bit on advertising and marketing (I'd go with Facebook Ads to start) and can "prove" there is market. In other words, your metrics can support a demand for your product - people respond to the ad, download the app and you can show app retention/growth. I would not rely on app store reviews and ratings as proof as those can easily be fabricated. However, real app metrics that you get from analytics and Flurry have meaning as they are based on data.
You dont need critical mass to show your concept is marketable and there is an audience, but you do need to take it to market first.
IMO, the only entrepreneurs who can secure funding based on a pitch deck without an MVP are ones that have a track record of starting and exiting other successful companies. Good luck!

This is a great question and one that I get asked at least once a week from entrepreneurs who want to build an app. I have a few quick words of advice:

1. You don't need a buisness plan, but a well though pitch deck is key. Guy Kawasaki has a great pitch deck plan: http://guykawasaki.com/the-only-10-slides-you-need-in-your-pitch/

2. Whether you are an novice or an expert, put your idea to paper. This can be in the form of user stories, bullet point features, hand drawn mock ups, screen shots from other apps - basically something to communicate to a developer what your idea is all about.

3. You need to spend some money to raise money. It doesnt have to be $100,000, but if you are serious about your idea and working with an app firm, be prepared to spend at least $5K to hire a team to flush out your concept and work with a UI/UX designer so that you can then present your idea to an investor. It is well worth it. My company has done this successfully for many start ups who then go on to secure a seed round of funding.

4. Your idea is not great. Everyone has "great" ideas. Its the execution of the idea, how thought through your idea is, who you end up choosing to work with to bring your idea to fruition.

5. Build an MVP to prove your assumptions and that your "great" idea has market value and you can gain users or customers. Dont focus on being everywhere at launch, focus on 1 platform (iPhone) and build it native. Pivot when you need to, be ready to abandon everything if you can't prove it. Read the "Lean Startup" before you do anything else.