A B2B SaaS can go from idea to its first invoice in the US with almost no fixed monthly cost in 2026. The stack:
- Incorporate a Delaware C-corp with Stripe Atlas ($500 once).
- Bank with Mercury (free plan).
- Bill through Stripe Billing (0.7% of volume) or Paddle (merchant of record, 5% + 50¢).
- Keep the books and taxes with Jupid (from $50/mo).
- Send product email through UniOne (4-month free trial, then from $6/mo).
- Measure usage with PostHog (1M events free each month).
- Run the pipeline in Attio (free up to 3 seats).
- Let Naoma AI demo the product to inbound visitors who arrive while you sleep.
The decisions that actually matter: who is merchant of record, and what you build rather than buy. This guide covers both.
We've shipped MVPs for founders since 2014, and this is the stack we see work. Prices are as listed on each vendor's site on 26 October 2026.
| Job | Tool | Starting price (Oct 2026) | Watch out for |
|---|---|---|---|
| Incorporate | Stripe Atlas | $500 once, then $100/yr | Delaware only; not legal advice |
| Bank | Mercury | $0 plan | A fintech, not a bank; 1% FX on non-USD wires |
| Bill | Stripe Billing | 0.7% of volume + card fees | You own sales-tax compliance |
| Books and taxes | Jupid | From $50/mo | US entities |
| Product email | UniOne | Free 4 months, then from $6/mo | You set up SPF, DKIM, DMARC |
| Analytics | PostHog | 1M events/mo free | Free plan: 1 project, 1-year retention |
| CRM | Attio | Free up to 3 seats | Free: 50k records, 200 emails/mo |
| Inbound demos | Naoma AI | From $249/mo, billed annually | Priced per engaged demo |
§ 01Incorporate: Stripe Atlas
If you plan to raise from US investors, the default is a Delaware C-corp. Stripe Atlas files it for $500 once. That covers state fees and the first year of a registered agent, then it's $100 a year. It also handles the EIN, the 83(b) election and founder equity, and gives you SAFE templates. The fee is refunded if you deposit $5k into Stripe Treasury within 90 days. It isn't legal advice: get a lawyer for the cap table the moment a term sheet appears.
§ 02Bank: Mercury
Mercury is where most US startups open their first account. The base plan is $0, with an API, cards and bill pay. Note that it's a fintech: the banking runs through partner banks (Choice Financial and Column N.A.). Watch the 1% FX fee if you pay contractors abroad.
§ 03Bill: Stripe Billing or Paddle
This is the first real architecture decision, and it's hard to reverse later:
- Stripe Billing costs 0.7% of billing volume on top of card fees (2.9% + 30¢ in the US). It's flexible for usage-based pricing, but you are the seller, so US sales tax and foreign VAT are your problem.
- Paddle costs 5% + 50¢ per transaction as merchant of record, and it handles tax collection and filing worldwide.
For a two-founder team selling self-serve globally, Paddle's premium often buys back weeks of compliance work. For sales-led annual contracts, Stripe is usually the better fit.
§ 04Books and taxes: Jupid
The bookkeeping you skip in year one becomes the tax problem in year two. Jupid is AI bookkeeping for US LLCs, freelancers and founders:
- It connects to the bank, categorizes every transaction (Jupid reports 95.9% categorization accuracy) and finds deductions.
- It prepares federal and state filings and quarterly estimates, with a CPA reviewing the return.
- You can ask it questions over WhatsApp or iMessage.
Plans start at $50 a month (Solo) and $200 a month (Team), and the company is SOC 2 Type II certified. It's built for owner-run US entities, so it suits the pre-revenue and early-revenue years before you hire a fractional CFO.
§ 05Product email: UniOne
Password resets, invites and invoices are product features, and a reset email that lands in spam is a support ticket. UniOne is an email API and SMTP service for transactional and marketing email:
- It has 200+ templates, webhooks, an email-validation API and dedicated IPs.
- It supports SPF, DKIM and DMARC authentication out of the box.
- It reports that 99.88% of its email reaches its destination.
The free trial runs 4 months at 6,000 emails a month. After that, Standard starts at $6 a month for 50,000 emails. Keep transactional email on its own sending domain, separate from any cold outreach.
§ 06Product analytics: PostHog
PostHog bundles product analytics, session replay, feature flags and experiments. The free allowance resets monthly: 1M events, 5K recordings and 1M flag requests, with unlimited team members. That covers most products well past launch. Instrument the activation event before launch day, not after.
§ 07CRM: Attio
Attio is the flexible CRM early B2B teams adopt when HubSpot's free tier feels cramped (HubSpot's free tier now caps at 2 users and 1,000 contacts). Attio is free for up to 3 seats, 50k records and 200 emails a month. Plus is $35 per seat per month, billed annually.
§ 08Demo while you sleep: Naoma AI
A US buyer who books a demo at 9 p.m. and waits two days often never shows up. Naoma AI puts an AI sales agent with a video avatar on your site:
- It runs a live, personalized demo of your product for every visitor or signup.
- It answers questions and objections in 80+ languages.
- It qualifies the lead and books a meeting into your CRM.
It learns from your sales scripts, recordings and docs. Pricing is per engaged demo, from $249 a month (billed annually) for 50 demos. That makes sense once inbound traffic exists, not on day one.
§ 09What to build yourself
Everything above is rented, and that's correct for the commodity layers. What you should build, and own, is the product:
- the workflow your buyer pays for;
- the integrations into their systems;
- the data model you'll still live with at Series A.
That's where we come in. Invental scopes and builds B2B MVPs in two-week sprints with staging from day one, and stays on for the first quarter after launch. Further reading:
- how we scope a project;
- why we start typed from day one;
- if you're preparing for a raise, pre-seed technical readiness and AWS startup foundations.