To frame the 5"x7" cards, go to Walmart, Target, etc. Do NOT use the 5"x7" frames as they cut off some of the image. Instead...
Purchase 6 of the 5"x7" (interior hole size) single mattes. The exterior size of these are 8"x10". Do NOT get the double mattes, or it cuts off the image. At this writing, they are about $1 each including tax.
Go pick out 6 8"x10" frames...make sure you get the ones with glass. Walmart has some nice oak or pine ones for $2-$2.50.
Tape cards into position from behind (top only, like a hinge) using cloth First Aid tape you will find in pharmacy. This stuff is usually fairly acid free because it has to not irritate injuries...

So for $6 (mattes); $13 (basic frame + tax); $1's worth of tape and $11 for set of cards =$30 you will have a nice set of 6 8"x10" framed prints.

Walmart also sells a very basic poster frame for about $10 that is 24"by 36". Cut the plexi down by scoring it with a sharp knife until it has a deep groove, and then line up the groove with the good part on a table and the off cut hanging over the side. You should be able to snap it off.
Now, cut down the 2 long plastic 'frame' channels with sharp scissors, make sure you allow for the corner angle.
DO NOT USE THE CORREGATED CARDBOARD. Splurge and get a thin piece of foam core or acid free matte board and cut it to 24" square.

Assemble, and for under $20, ($30 including the poster) Voila!