Recommended white label website builder?

I'm hoping that some of you guys might have a solid recommendation for a white label website builder (that you've actually used). One of my many startup ideas involves offering a particular niche with a particular bundle of products. I'm not going to go into the niche or model for obvious reasons but it revolves around providing an easy click and drag site builder that requires no previous experience of knowledge of coding for the end user. I've looked at DevHub which looks very promising but the initial setup costs are hefty at 2K plus $500 per month with an additional $4 per site per month. Weebly is another option which seems a lot simpler but it's not as flexible as I want. I really need the ability to offer my own set of custom templates to my users, also full rebranding is an absolute requirement. Integration with 3rd party tools etc through an auto installer script would be nice but not a deal breaker. DevHub looks great but quite frankly the base setup costs (including 3rd party design) for year one at less than 500 users is about 25K which increases the risk and makes cash flow for expansion difficult. I'd rather not have to look for angel investment to get this project off the ground so a more economical alternative is what I need. All of my cashflow is pretty much tied up in a larger project so this is what you would call a typical 'lean startup'.
I know it's a tall order but any suggestions would be really welcome.
Thanks,
Dave