Visit your local museum/art gallery on those clutch "free" days
If you want to treat your date to something a little posh -- without breaking your nonexistent bank account -- there’s usually at least one free museum or art gallery in your town or city. Pay-to-play museums and art galleries usually also offer a day when they will accept donations instead of general admission fees.
I can attest that this is a killer date idea; but unless you were a fine-arts major, sometimes strolling through a museum can be boring. You can make it interesting by reading up on one of the exhibits ahead of time so you have something to talk about and critique. Or, if you're the playful type, create a scavenger hunt. Make a list of things for you and your date to find in paintings -- flowers, birds, horses (there’s always a shit-ton of horses) -- and whoever finds everything on their list first wins.
Have yourselves a massage night
For a ridiculously amorous and inexpensive date (but NOT A FIRST DATE by any means!), treat your SO to an at-home, pampering massage. Beforehand, purchase some sensually scented body oils or lotion from the local drugstore. Later that night, light some candles and play soothing New Age music that isn't overly obnoxious while treating your sweetie to a romantic rubdown from head to toe. If you’re lucky, she’ll return the favor. Draw a warm bath afterward for the two of you and then get down with some soaking sexy times.
Really, though, this is for people who are already couples. Don't be that creepster who suggests such a night for the third (or first!) date.
Netflix and... well, you know
Staying home to binge-watch the latest Netflix obsession is a pretty obvious choice. But snuggling under blankets while sharing a mutual admiration for Bloodline’s Kyle Chandler over a frozen pizza is still a good time. Back when I was a broke 20-something and Netflix was still strictly a DVD-by-mail company, my boyfriend and I frequently would stay in, watch Willow, and have sex.
I had no complaints.
Which brings up the other obvious point about the Netflix-and-chill phenomenon: it's the best way to ensure getting laid.