DIY and Household blogger Ana White's site shares an easy-to-construct DIY couch that offers two large storage spaces beneath the seat. Normally DIY couches are expensive due to buying upholstery foam, but this design uses a 7.6cm thick camping mattress as the seat.
Full plans, photos, and step-by-step directions can be found at the source link below, but you'll need 5.4m of upholstery, 2.28m of burlap, pillow stuffing, two sheets of 0.63cm plywood, and around eight boards in various sizes. Plan to spend around $US100 plus the camping mattress which the author found for $US30 but can vary widely. Twin bed mattress toppers would probably work fine as well.
You'll need basic woodworking and sewing skills, but the project doesn't require any fancy wood cuts or stitches so it should be easy to build for novices.
When you're finished you'll have a cozy, sturdy couch that looks modern and has two storage compartments that measure 68.5 x 88.9 x 25.4cm which is perfect to hold pillows and blankets to use the couch as a guest bed.
Storage Sofa [Ana White Homemaker]