The options are the same as buying many traditional businesses.
You can obviously use your own funds, raise funds from friends and family, use personal lines of credit, crowdfunding/investment or seek personal loans from financial institutions.
Any wise investor in your venture should require -- and you should have prepared -- financials for the online business you are purchasing. Does the online brand have tangible assets? Inventory? Existing sales/AR? What about long-term purchase orders or contracts?
Where I see most entrepreneurs stumble is buying too much into "blue sky" value, that is, believing the sellers opinion of what future value the brand/company may have. You have to take that into consideration, but it should not be "the" deciding factor. If the business is truly a cash cow, as many buyers would want you to believe, why are they selling it? Do you see opportunity for growth? What skill set or leverage do you have that will accelerate that growth or expand the market of your acquisition?
Again, funding options are generally the same between traditional businesses and online businesses. Investors/lenders will require the same due diligence and financials to establish an assess the level of risk.
All the best,
I've sold a number of SaaS businesses and acquired a software business in October.
There are several main avenues:
1. Self-fund - Either take money out of your own pocket, or sell assets you own
2. Take a loan - Friends, family or banks. Expect lower amounts from friends and family (depending on what circles you travel in), but more favorable repayment terms. Flip that around for banks.
3. Take on a funding partner - Give someone a piece of equity in return for them investing their funds into the biz
4. Bootstrap with profits from another business - Use cashflow generated by another business to finance your next acquisition
5. Earn-out option - I've heard of some folks setting up a deal with the owner of the business where they pay a partial sum to acquire the business, then pay a portion (or all) of the subsequent monthly profit after ownership changes hands, for either a defined amount of time, or up to a certain amount to the previous owner, in order to "earn out" the rest of the balance due.
6. Find a suitcase full of cash down by the river ;)
7. Work-to-own - Going out on a limb here, but if you were in possession of a skillset that was valuable to the business, you could conceivably offer to work for equity, instead of getting paid for your time. Strictly a theoretical scenario, but I'm just thinking outside the box here.
I hope that helps! Feel free to gimme a call if you have more questions about this. ~Jason