1. In my experience B2B ideas are best for quick monetization compared to B2C.
2. Think of roadblocks you face creating your own site. Pretty sure somebody else will face them too (many great products were created out of this, readme.io, statuspage, etc)
3. Don't go all in. I never spend more than 2 weeks before submitting my project on PH, HN, mailing my list. Don't ever make the mistake of working on something for 2 years alone not telling anyone about it.
4. Don't reinvent the wheel. Ie don't waste time on things like your login page (HNs login page is a great example on how much it matters), hiring designers (a template from HTML5rocks or wrapbootstrap is just as good). A lot of these things (support, auth, chat, etc) are offered as Saas services and can be integrated directly to save you weeks in launch.
5. Marketing is where you want to spend most of your time since yoh ask about making money. Also don't be afraid of pricing. Read patio11 black art of saas pricing for an excellent guide. Learn content marketing, SEO, etc.
Good luck!