Are there sides at same-sex wedding ceremonies?
It's up to the couple. Some pairs opt to set sides for their families, while others prefer for guests to sit wherever they'd like. You and your future spouse should decide which option you're most comfortable with before you start planning, then make that decision known to your planner and any wedding VIPs who will help guests get to their seats.
As you make your decision, think about these important factors. Do you and your future spouse share many of the same friends, or do you have very different social circles? Are you inviting a large number of extended family members on each side, or are you planning to keep the celebration a bit more intimate? These are questions that are worth asking for any wedding, but especially so when there are two brides or two grooms, making the traditional ceremony structure a bit different.
Guests shouldn't worry too much about sitting on the wrong side. If the couple chooses sides, the wedding's ushers (should they have them), will let attendees know where to go. Other couples will inform guests about seating with a sign. Some popular phrasing options are, "Choose a seat, not a side, either way it's for a bride" or "Groom's side and Groom's side."
Who pays for a same-sex wedding?
It's a pretty old-school thought that the parents of the bride would pay for the whole wedding, so that likely won't be the case with any modern wedding, whether or not it's for a same-sex pair. Most couples end up compiling funds from a few different sources. The couple themselves may provide the majority of the budget, while families on either side may pitch in a bit as well.
Should one of us take the other's last name?
You have lots of options. Changing your name is a surprisingly long and tedious process, but it may be something that feels meaningful and worth the time and effort for you. If so, there's not a particular formula in place. You might both go with a hyphenated version of your names or select one name over the other.
Do we have to invite guests who don't support our relationship or same-sex marriage in general?
It's up to you. If a family member has blatantly told you they don't support your relationship, it'd be hard to come up with a reason to invite them. But sometimes the act of extending the invitation is a sort of peace offering, giving an opportunity for that family member to rethink their position.