It's hard to imagine the benefits of being a hobo (or tramp), but for Halloween, there are several.
The homemade costume is cheap because you can use clothing you already have or can find in a thrift store. There's no need to go shopping or worry about what you want not being available (great for a last minute costume idea). You can also adjust your attire to the weather so that you are more comfortable.
The fun thing about dressing up as a hobo is that the "costume" is androgynous. If you're creative, you will have people guessing whether you're really a guy or gal. Kind of like those old Saturday Night Live skits with "Pat". The ideas below will work great for a hobo, bum, vagrant, or vagabond. You can call it what you want. Add a sign and you can be a beggar. Just remember to "act" the part with your demeanor. You might want to slouch, act miserable, and shuffle when you walk.
Old clothes are great because they're probably already worn and faded. A button-up, long-sleeved flannel shirt with faded blue jeans or painter's pants is a good start. You can wear overalls if you wish but then you risk looking like a stereotypical farmer. To look like an authentic hobo, add some tears, patches, and dirt to your attire.
If you plan on adding stuffing to make yourself look heavier, you'll need to find clothing that is roomy, perhaps one size too big. You can use a pillowcase to hold the stuffing and secure it to the inside of your clothing with safety pins. Small pillows used for camping are great for kids and they're already stuffed.
Shoes & Hat
There's no certain type of shoes that hobos or bums wear. Work boots, an old pair of sneakers, military boots, or any old pair of shoddy shoes will work with your costume. As far as a hat goes, look for an old straw hat (avoid wearing a cowboy hat if you can) or a baseball/bill cap worn backwards (can also be used to contain long hair). Do what needs to be done to make it look tattered. Run it over with the car if necessary!
Find a long stick and attach a bandana with stuffing with string on the end for your hobo stick. This should be carried over the shoulder and represent the few belongings that you have. For a beggar look, carry a sign asking for money. Poster board or cardboard works well. Use a permanent marker or one that will not run if it gets wet. Be humorous with your message and make sure that your sign is a size that is easy to carry and does not obstruct your view.
Use an old pillowcase, small burlap bag, or reinforced brown paper sack (double it for strength) for a treat bag.
You can apply makeup to change your appearance. A dark brown or black eyebrow pencil can be used to make your eyebrows bushy or draw in a moustache, beard, and sideburns if desired. Lipstick liner can be used to add a few fake wrinkles and blemishes. Remember, stereotypical hobos look older than their true age, a result of poor nutrition and lifestyle.