Earlier quoted context omitted.
I did it for 5.7 years (for health reasons, not to save a few bucks), though I did not camp on a sidewalk and I did freelance work instead of having a job. I don't recommend it. I also doubt that you would save as much as you think.
Would I be able to ask some questions? What health reasons would cause you to sleep in a tent that doesn't involve saving money? And where did you sleep? And why not sleep in a vehicle? And why did you not save as much as you thought? By the way, if you want to live in a vehicle, tent or something like that while freelancing, you could always just move to Eastern Europe, India or someplace else and live well for what…
I slept in a tent in whatever greenery I could find, usually on the edge of town. The reason I did not sleep in a vehicle: I gave up my car years before I went homeless. I no longer drive.
I didn't say I didn't save money. I said the OP likely would not save as much as they think.
OP said they would save $3000/mo. Let's assume that is current rent.
Housing is a place to store all your stuff. Many homeless people rent a storage unit for their stuff. Subtract the cost of your storage unit.
Housing allows you to buy food cheaply and cook from scratch. No kitchen means buying a lot of prepared stuff from eateries. If you are suddenly "saving" $3k/mo, you probably will not be eating at the absolute cheapest places to save money. Subtract higher food costs from your savings.
If you have a regular job, you need to be presentable. Homeless showers are often pretty horrifying and their schedules are incompatible with most work schedules. Most people will need to pay for some kind of shower access, such as a gym membership, truck stop showers and/or the occasional motel stay. Subtract that from your savings.
You can't expect to leave anything in your tent. It isn't secure. You have to carry everything you own everywhere at all times to secure it. If you leave your tent on the sidewalk, it may be gone when you get back. If you have money, you can potentially buy expensive lightweight, ultra slim items to make your alternative lifestyle work, such as a silk sleeping bag liner instead of heavier bedding. Subtract those expenses from your savings.
Camping tents are not intended to be lived in. They wear out when you live in them full time. I replaced my tent every one to three months. Subtract that from your savings.
Seattle is very wet. Cheap tents are never very waterproof. You either need a more expensive tent or to accept that stuff will be ruined or to check into a hotel anytime it rains hard. When electronics, like a phone or laptop, get wet, they can die. Life on the street is hard on possessions. They routinely get lost, broken or stolen. Subtract that from your savings.
Etc.
I could probably go on, but that should give you some idea.