Factoring is not a decision to be taken lightly. I'd consider getting the help of an independent financial advisor before undertaking it. Once you’ve started factoring it’s quite difficult to stop. However, I’ve seen it worth quite successfully for manufacturing businesses that need to buy expensive materials to manufacture finished products.
Putting a business plan together for any potential investor is no small undertaking. The business link site in the UK had some good guides and templates (it’s now www.gov.uk), but I’d strongly consider getting some help to put your plan together. Some accountants and investors offer a free business plan review service which we found useful for an initial sense check of the first draft.
It will be worth checking if there are any local grants or schemes in the area that can help you get started; most of these in the UK appear to have dried up or are not worth the effort (as the grant is only small - about £500 in some areas).
If you’re considering venture capital or approaching angel investors, I’d seriously consider what you’ll have to give up as a share of your business to get this money and if there is the option to grow organically Vs the money and the knowledge you could get from a venture capitalist.
Should you be considering a loan of some sort, you may need to think about the risks of an equity loan as if the funding you require is substantial the lender may require some form of personal guarantee (which is usually your home or premises).
Google+ is good and quite low maintenance if you just put links to your new pages and updates.
I find guest blogging to be a slow burn as you have to build a relationship with the site owner to be allowed to blog. Personally, I wouldn't bother with the likes of Ezines and PRweb as everyone uses them and they don't offer anything that's particularly unique.
Finding a blog/site that's related to your business always seems to work best in my experience, particularly if they have some form of editorial content.
emailing prospects is free, even with MailChimp if your list is smaller than 2,000 and you are sending less than 12,000 emails a month.
The cost will come in buying the contact data if you don't have it already. You might be able to go the public library and scan/photocopy the stuff out the business directories they have in there.