I'm not a lawyer and this is not legal advice.
I recommend finding a lawyer and an accountant that specialize in crowdfunding. Legislations on crowdfunding is constantly changing so keeping up with it on your own will be a nightmare.
These types of platforms are still relatively new so It might be hard to find reputable ones with good track records.
If you would like help finding reputable lawyers and accountants that specialize in crowdfunding, I can help you with your research.

Are you looking into making crowdfunding your business model or are you trying to raise money for a certain cause? What's the purpose of the platform? That impacts all other matters.

Hello there,

For crowdfunding platforms you need to look at your idea from different perspective. there are a lot of things which need to be considered, from agreement sections that decrease number of scammers who join your website to UI and UX. Here are some friendly advice:

1 - There are big competitors like kickstarter and indiegogo out there in this market so you need some type of special difference to make your platform unique to be able to compete with them

2 - Make a targeted community on social networks(I can help you with that if you want) to have a marketing pool

3 - Try to find some innovative ideas to start your platform with them or start it with your own ideas

If you need any help or have further questions, please do not hesitate to send me a message here

You need to ensure that you build into te platform a mechanism to establish who the funders and recipients really are so that you do not become a money laundering/ terror financing point. You have to know with a high confidence level who the source of funds is and who the ultimate payee is.