Here are some practical tips for long term travel. This is all written from the perspective of someone living in the US, but many tips apply universally.
Get an unlocked phone and buy a pre-paid SIM card in every country you visit. This is a fraction of the cost of using your US SIM card internationally. A SIM card is usually between free and US$5. Credits for Internet data or voice calls varies, but you can usually find something cheap. In Europe particularly do some research first as rates per GB / minute vary enormously. Ask the vendor to install and activate the SIM card (often very non-trivial) and explain how to add credit, every company has a different way.
Open a free Google Voice account. That way, you have a stable US phone number on which you can receive voice calls and text messages no matter where you are in the world. Google will transcribe voice mails to text and forward them to your gmail email. Text messages (= SMS messages) are also forwarded to your gmail email. A stable US phone number for receiving text messages is essential for two factor authentication when logging into websites.
Get a Voice over IP (VOIP) application on your phone and maintain some balance on it. There are many, but I like KeepCalling. Making international calls on a VOIP application is a fraction of the cost (a cent or two per minute). Note that most VOIP services cannot receive text messages (Google Voice is the exception).
WhatsApp allows you to keep using your old cell phone number even when your cell phone number changes due to a new SIM card.
You need a stable US address to receive snail mail. There are many mail services. I use Traveling Mailbox and I am very happy with them. They provide a real address, not a PO box. They scan the envelope of every received mail. You can choose to open and scan the contents, forward, hold, destroy, or cash a check. Everything happens online or using a smartphone app. Prices are reasonable and online support is outstanding.
ATM and Credit Cards
Get a card that does not charge fees for International credit card transactions or ATM withdrawals – these add up quickly.
Cary cards from multiple banks in case one is refused or gets blocked.
Make sure you register travel plans with your bank. Most provide an online way of doing this.
Make sure you have the phone number of the fraud prevention department of your bank. You will need to call them to unblock your card after your bank erroneously blocks it (even when you register your travel plans). Keep in mind that you cannot call toll-free US numbers from abroad (unless you have a VOIP app).
Get a credit and debit card with a chip. Many countries require them. Some places in Europe don’t even accept cash anymore.
Get a card with a PIN code and know what it is. It is required in many places. The practice of signing a receipt is unheard of in some places.
Make sure your cards are valid for the entire duration of the trip. Renew before you leave if necessary.
Your bank may send you a replacement card and cancel your current one out of the blue when they suspect fraud. Make sure you have a way of forwarding it to you when that happens (see mail chapter).
Activate your online banking. Your bank will not have offices abroad and it is nearly impossible to get them to do anything over the phone.
Use a two factor authentication method that will work abroad. Bring your token. Or install a soft-token app on your phone. Get Google Voice so you can receive SMS message no matter where you are.
Remember that US citizens are required to file taxes no matter where they live. Get an accountant that understands residency rules well and that can interact with you remotely.
Travel light. You can buy whatever you need along the way, probably cheaper. Exception: good camping gear is difficult to find in developing countries and expensive in Europe.
Bring an Amazon Kindle Paperwhite. All your books in a few ounces. Great battery life and can read at night.
If you trek in remote areas, get a Garmin (formerly DeLorme) InReach. It is essentially a satellite phone on which you can send and receive text messages from anywhere in the world even if there is no cell phone coverage.
Let friends and family know where you are and plan to be. I do a daily checkin on my InReach and post my plans on a shared Dropbox folder.
Put copies of all your papers (e.g. Passport) in a secure place in the cloud (e.g. Dropbox) .
Bring an external battery pack for your devices.
Web / Apps
Many websites require two factor authentication when you move to a different country. Use Google Voice to receive text messages (see above)
Use a VPN to pretend you are in the US. This helps to avoid two factor authentication issues or to avoid location restrictions (e.g. to download Amazon Prime movies). There are many but I like ExpressVPN.
Google Maps and maps.me allow you to download maps for free, so that you can navigate even without coverage. Get both – they complement each other.
Use an app (e.g. Google Photos or Apple Photos or Flickr) to backup your photos in the cloud.
Use wikiloc to discover off-the-beaten-track hikes.
What to do with your house back home? One option (my vote) is to sell it if (if you own it) or cancel the lease (if you rent it). Another option is to rent it out. I did this once too. It provides income but do not underestimate the burdens of being a remote landlord – get a good managent company (easier said than done – most suck).